Accessory, interchangeable lens and camera body

ABSTRACT

An accessory includes: a clock transmission unit that transmits a first clock signal; a first transmission unit that transmits to the camera body information pertaining to a drive target member in synchronization with the first clock signal; a clock reception unit that receives a second clock signal from the camera body; a second transmission unit that transmits to the camera body a first value indicating a communication specification according to which the first transmission unit transmits the information to the camera body in synchronization with the second clock signal; a reception unit that receives from the camera body a second value in synchronization with the second clock signal, indicating a communication specification; and a control unit that engages the first transmission unit to start transmitting the information according to the communication specification indicated by the second value, upon receiving the second value after the first value has been transmitted.

INCORPORATION BY REFERENCE

The disclosure of the following priority application is hereinincorporated by reference: Japanese Patent Application No. 2018-135120filed Jul. 18, 2018.

TECHNICAL FIELD

The present invention relates to an accessory, an interchangeable lensand a camera body.

BACKGROUND ART

A camera system in the related art allows an accessory, a typicalexample of which is an interchangeable lens, to be mounted at a camerabody. Optimal data communication needs to be carried out between such anaccessory and the camera body.

CITATION LIST Patent Literature

PTL 1: Japanese Laid Open Patent Publication No. 2016-85423

SUMMARY OF INVENTION

According to a first aspect of the present invention, an accessory thatis mountable at a camera body and is capable of communicating with thecamera body, comprises: a clock transmission unit that transmits a firstclock signal to the camera body; a first transmission unit thattransmits to the camera body information pertaining to a drive targetmember that is driven by a drive unit in synchronization with the firstclock signal; a clock reception unit that receives a second clock signalfrom the camera body; a second transmission unit that transmits to thecamera body a first value indicating a communication specificationaccording to which the first transmission unit transmits the informationto the camera body in synchronization with the second clock signal; areception unit that receives from the camera body a second value equalto or smaller than the first value in synchronization with the secondclock signal, the second value indicating a communication specificationaccording to which the first transmission unit transmits the informationto the camera body; and a control unit that engages the firsttransmission unit to start transmitting the information according to thecommunication specification indicated by the second value, uponreceiving the second value by the reception unit after the first valuehas been transmitted by the second transmission unit.

According to a second aspect of the present invention, an accessory thatis mountable at a camera body and includes a plurality of terminals viawhich communication is carried out with the camera body, comprises: afirst terminal through which a first clock signal is output to thecamera body; a second terminal through which information pertaining to adrive target member that is driven by a drive unit is output to thecamera body in synchronization with the first clock signal; a thirdterminal through which a second clock signal is input from the camerabody; a fourth terminal through which a first value is transmitted tothe camera body in synchronization with the second clock signal, thefirst value indicating a communication specification according to whichthe information is transmitted through the second terminal to the camerabody; a fifth terminal through which a second value is received from thecamera body in synchronization with the second clock signal after thefirst value is transmitted through the fourth terminal, the second valueindicating a communication specification according to which theinformation is transmitted through the second terminal to the camerabody; a sixth terminal used to indicate whether or not communicationwith the camera body is enabled; a seventh terminal through which asecond source voltage from the camera body is supplied; an eighthterminal used as a ground potential for the second source voltage; aninth terminal through which a first source voltage from the camera bodyis supplied; a tenth terminal used as a ground potential for the firstsource voltage; an eleventh terminal used for the camera body to detectthat the accessory is mounted; and a control unit that startstransmission of the information through the second terminal according tothe communication specification indicated by the second value uponreceiving the second value through the fifth terminal.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram presenting an example of a structure that may beadopted in a camera according to a first embodiment.

FIG. 2 shows a chart in reference to which command data communicationexecuted in the camera in the first embodiment will be explained.

FIG. 3 is a schematic diagram illustrating electric connections achievedat a lens-side connection unit and a body-side connection unit in thefirst embodiment.

FIGS. 4A and 4B show schematic illustrations of a camera body mount inthe first embodiment, viewed from the side where an interchangeable lensis located.

FIG. 5 is a schematic illustration of an interchangeable lens mount inthe first embodiment, viewed from the side where the camera body islocated.

FIG. 6 shows a chart presenting examples of different generationsaccording to the first embodiment.

FIG. 7 shows a chart presenting examples of generations that may beselected in the camera in the first embodiment.

FIG. 8 shows a chart presenting examples of generations that may bedetermined in the camera in the first embodiment.

FIG. 9 shows charts presenting an example of processing andcommunication that may be executed in the camera in the firstembodiment.

FIG. 10 is a diagram presenting an example of a method that may beadopted when calculating a time length Δt in the camera in the firstembodiment.

DESCRIPTION OF EMBODIMENTS First Embodiment

FIG. 1 is a diagram showing a structure that may be adopted in a camera1 achieved as an example of an image capturing device in the firstembodiment. The camera 1 is configured with a camera body 2 and aninterchangeable lens 3 that is an attachable accessory. The camera 1,configured with the camera body 2 and the interchangeable lens 3 asdescribed above, may be otherwise referred to as a camera system.

A body-side mount unit 201, at which the interchangeable lens 3 ismounted, is disposed at the camera body 2. A lens-side mount unit 301,which is mounted at the camera body 2, is disposed at theinterchangeable lens 3. A lens-side connection unit 302 and a body-sideconnection unit 202 are respectively disposed at the lens-side mountunit 302 and at the body-side mount unit 201. The lens-side connectionunit 302 and the body-side connection unit 202 each include a pluralityof terminals or contacts such as clock signal terminals, data signalterminals and power supply terminals disposed therein, as will bedescribed later. The interchangeable lens 3 is detachably mounted viathe lens-side mount unit 301 at the body-side mount unit 201 of thecamera body 2.

As the interchangeable lens 3 is mounted at the camera body 2, theterminals disposed at the body-side connection unit 202 and theterminals disposed at the lens-side connection unit 302 becomeelectrically connected. As a result, it becomes possible to provideelectric power from the camera body 2 to the interchangeable lens 3 andto carry out communication between the camera body 2 and theinterchangeable lens 3.

The structure of the interchangeable lens 3 will be first described indetail. The interchangeable lens 3 includes a photographic opticalsystem 31, an aperture stop 32, a lens drive unit 33, a lens positiondetection unit 34, an aperture drive unit 35, a lens memory 36 and alens control unit 37. While the photographic optical system 31 isrepresented by a single lens so as to simplify the illustration, it isactually constituted with a plurality of lenses including a focus lens(focus adjustment lens) and as the interchangeable lens is mounted atthe camera body 2, a subject image is formed on the image capturingsurface of an image sensor 21 via the photographic optical system 31.The photographic optical system 31 may include, for instance, a zoomlens via which the focal length can be varied or an anti-vibration lens(shake-correction lens or blur-correction lens) that reduces the extentof image blurring (attributable to hand movement) as well as the focuslens (focus adjustment lens). It is to be noted that the aperture stop32 is actually disposed, for instance, among the plurality of lenses inthe photographic optical system 31.

The lens drive unit 33 and the aperture drive unit 35 may each beconfigured with, for instance, a stepping motor, an ultrasonic motor, aDC motor or the like. The lens drive unit 33 controls drive of thephotographic optical system 31. The lens drive unit 33 alters the imageforming position at which the subject image is formed via thephotographic optical system 31 by causing the focus lens to move alongan optical axis L based upon, for instance, a signal output from thelens control unit 37. In addition, the aperture drive unit 35 alters theopening diameter of the aperture stop 32 by driving the aperture stop 32based upon a signal output from the lens control unit 37. It is to benoted that in conjunction with a photographic optical system 31 thatincludes a zoom lens and an anti-vibration lens, the lens drive unit 33may include drive sources to drive the zoom lens and the anti-vibrationlens via the respective drive sources. In such a case, the lens driveunit 33 will move the zoom lens along the optical axis L based upon asignal output from the lens control unit 37. In addition, the lens driveunit 33 will move the anti-vibration lens along directions intersectingthe optical axis L based upon a signal output from the lens control unit37.

Furthermore, the lens drive unit 33 and the aperture drive unit 35 mayeach include a drive circuit (e.g., a drive IC) (not shown) that drivesthe stepping motor, the ultrasonic motor, the DC motor or the like.

The lens position detection unit 34 may be configured with, forinstance, a photo-interrupter and an encoder. The photo interrupterdetects a passage of a detection target portion (e.g., a focus lenssupport portion) of the photographic optical system 31 through areference position (origin point position) on the optical axis L andoutputs a detection signal to the lens control unit 37. Based upon thesignal output from the photo interrupter, the lens control unit 37detects a passage of the focus lens through the reference position(origin point position). The encoder, constituted with a linear encoder,generates at least two pulse signals assuming phases different from oneanother and detects the distance over, and direction along which, thefocus lens moves based upon the two or more pulse signals. The distanceover which the focus lens has moved, having been detected, is output asa pulse signal to the lens control unit 37. As an alternative, amagnetic encoder or the like may be utilized and a pulse signalcorresponding to the absolute position may be output.

It is to be noted that when a stepping motor is used as the lens driveunit 33, a passage through the origin point position may be simplydetected via a photo interrupter without utilizing an encoder. In such acase, as the detection target portion (e.g., a focus lens supportportion) of the photographic optical system 31 passes through the photointerrupter of the lens position detection unit 34, a signal indicatinga passage of the photographic optical system 31 through the origin pointposition will be output to the lens control unit 37. A pulse signalcorresponding to the extent to which the lens is to be moved is outputfrom the lens control unit 37 to a stepping motor drive circuit in thelens drive unit 33 and also a pulse signal, which corresponds to thepulse signal output from the lens control unit 37 to the drive circuitin the lens drive unit 33, corresponding to the extent of the lensmovement, is output from the drive circuit in the lens drive unit 33 tothe lens control unit 37, so as to drive the photographic optical system31.

It is to be noted that when the photographic optical system 31 includesa zoom lens or an anti-vibration lens, the lens position detection unit34 detects the extent of movement with respect to the zoom lens or theanti-vibration lens and generates a signal indicating the extent of zoomlens movement or the focal length of the zoom lens or a signalindicating the extent of anti-vibration lens movement or the position towhich the anti-vibration lens moves.

The lens control unit 37, which is constituted with a processor such asa CPU, an FPGA or the like and a memory such as a ROM, a RAM or thelike, controls the various components of the interchangeable lens 3based upon a control program. The lens control unit 37 controls drive ofthe photographic optical system 31 and the aperture stop 32 via the lensdrive unit 33 and the aperture drive unit 35 based upon control signalsinput thereto from a body control unit 27 in the camera body 2 via thebody-side connection unit 202 and the lens-side connection unit 302. Forinstance, in response to a control signal indicating the direction alongwhich, and the distance over which, the focus lens is to move, the speedat which the focus lens is to move and the like input thereto from thebody control unit 27, the lens control unit 37 issues an instruction forcontrolling drive of the lens drive unit 33 based upon the controlsignal.

In addition, the lens control unit 37 detects the position of the focuslens, the zoom lens or the like and transmits the detection results tothe camera body 2. When a stepping motor is used as the lens drive unit33, the lens control unit 37 transmits an instruction indicating theextent to which the focus lens is to be driven to the lens drive unit33. The drive circuit (not shown) in the lens drive unit 33 drives thestepping motor accordingly. As the stepping motor is driven, a pulsesignal corresponding to the extent of drive is output from the drivecircuit in the lens drive unit 33 to the lens control unit 37.

Based upon an output provided from the photo interrupter in the lensposition detection unit 34, the lens control unit 37 senses a passage ofthe focus lens or the zoom lens through the reference position (originpoint position), and further generates information (pulse positioninformation) corresponding to the extent of focus lens movementrepresented by a cumulative value calculated by counting pulse signalsinput thereto from the encoder or pulse signals corresponding to theextent of stepping motor drive.

The information corresponding to the extent of focus lens movement(pulse position information) thus generated is transmitted to the camerabody 2 through hotline communication, which will be explained later.

The lens memory 36 may be constituted with, for instance, a non-volatilestorage medium. Various types of information pertaining to theinterchangeable lens 3 are stored in the lens memory 36. For instance,information such as the focal length, the maximum aperture number at theinterchangeable lens and information indicating communicationspecifications or communication conditions that can be supported by theinterchangeable lens 3 when it carries out communication with the camerabody 2 are stored in the lens memory 36. The information indicating thecommunication specifications will be referred to as an interchangeablelens generation, as will be explained later. An alternative term“generation information” may be used instead of “the generation”. Thegeneration information pertaining to the interchangeable lens 3 will bereferred to as lens-side generation information. Data write into thelens memory 36 and data readout from the lens memory 36 are controlledby the lens control unit 37. It is to be noted that the lens-sidegeneration information may instead be stored in an internal memory builtinto the lens control unit 37.

In addition, the lens control unit 37 includes a first lenscommunication unit 38 and a second lens communication unit 39. As willbe described in detail later, the first lens communication unit 38 isengaged in command data communication with a first body communicationunit 28 via the lens-side connection unit 302 and the body-sideconnection unit 202. The second lens communication unit 39 is engaged inhotline communication with a second body communication unit 29 via thelens-side connection unit 302 and the body-side connection unit 202.

Next, the structure of the camera body 2 will be explained in detail.The image sensor 21, a body memory 22, a display unit 23, an operationunit 24, a power supply unit 26 and the body control unit 27 aredisposed at the camera body 2. The body control unit 27, which isconfigured with a processor such as a CPU, an FPGA or the like, and amemory such as a ROM, a RAM or the like, controls the various componentsof the camera 1 based upon a control program.

The body control unit 27 generates image data by executing predeterminedimage processing on signals output from the image sensor 21. Such imageprocessing includes image processing of the known art such as, forinstance, gradation conversion processing, color interpolationprocessing and edge enhancement processing. The body control unit 27also generates control signals used to control drive of the photographicoptical system 31 (focus lens drive, zoom lens drive and/oranti-vibration lens drive) and drive of the aperture stop 32.

Furthermore, the body control unit 27 executes processing required forautomatic focus adjustment (AF) for the photographic optical system 31.In more specific terms, the body control unit 27 executes focusdetection processing by adopting a phase detection method. The imagesensor 21 includes focus detection pixels each having part of aphotoelectric conversion unit within the pixel shielded with alight-blocking film, disposed in place of some of image capturing pixelsthat output image capturing signals. The body control unit 27 calculatesa defocus quantity representing an extent of defocus through the phasedetection method by using focus detection signals output from the focusdetection pixels. The body control unit 27 outputs a signal pertainingto the defocus quantity having been calculated, to the lens control unit37. The lens control unit 37, in turn, drives the focus lens incorrespondence to the defocus quantity. It is to be noted that the imagesensor 21 may adopt a structure that includes image capturing/focusdetection pixels, each having a plurality of photoelectric conversionunits disposed therein and capable of outputting both an image capturingsignal and a focus detection signal.

Moreover, the body control unit 27 may execute focus detectionprocessing through a contrast detection method instead of focusdetection processing executed through the phase detection method or inaddition to focus detection processing executed through the phasedetection method. Namely, the body control unit 27 may sequentiallycalculate subject image contrast evaluation values based upon signalsprovided from the image sensor 21 while moving the focus lens in thephotographic optical system 31 along the optical axis L. The bodycontrol unit 27 engaged in this focus detection processing then setseach contrast evaluation value in correspondence to a specific focuslens position by using focus lens position information (pulse positioninformation) transmitted from the interchangeable lens 3. The bodycontrol unit 27 then calculates an in-focus position for the focus lens.The body control unit 27 outputs a signal corresponding to thecalculated in-focus position to the lens control unit 37. The lenscontrol unit 23, in turn, moves the focus lens to the in-focus position.

The power supply unit 26, which includes a power source, supplieselectric power to components within the camera body 2 and to theinterchangeable lens 3. The power supply unit 26 is connected to thebody-side connection unit 202 and the body control unit 27. The powersupply unit 26 provides electric power to the lens control unit 37 viathe body-side connection unit 202 and the lens-side connection unit 302.

The image sensor 21 may be, for instance, a CMOS image sensor or a CCDimage sensor. The image sensor 21 receives a light flux having passedthrough the photographic optical system 31 and captures a subject image.The image sensor 21 includes a plurality of pixels each having aphotoelectric conversion unit, disposed thereat in a two-dimensionalpattern along a row direction and a column direction. The photoelectricconversion unit may be constituted with, for instance, a photodiode(PD). The image sensor 21 generates signals through photoelectricconversion of the light received thereat and outputs the signals thusgenerated to the body control unit 27.

The body memory 22 may be constituted with, for instance, a non-volatilestorage medium. A program based upon which the camera body 2 and thecamera 1 are controlled is stored in the body memory 22. In addition,information indicating a camera body generation, to be explained later,i.e., information indicating communication specifications that can besupported by the camera body 2 when carrying out communication with theinterchangeable lens 3, is also stored in the body memory 22. Theinformation indicating the communication specifications is otherwisereferred to as a camera body generation, as will be explained later.Such a “generation” may be alternatively referred to as generationinformation. The generation information pertaining to the camera body 2will be referred to as body-side generation information. Data write intothe body memory 22 and data readout from the body memory 22 arecontrolled by the body control unit 27. It is to be noted that imagedata may be stored in the body memory 22 or they may be stored into aseparate storage medium. In addition, the body-side generationinformation may be stored into an internal memory built into the bodycontrol unit 27, instead.

At the display unit 23, an image is displayed based upon image data, andinformation pertaining to a photographing operation such as shutterspeed, aperture stop setting and the like, a menu screen and the likeare also brought up on display at the display unit 23. The operationunit 24, which includes a shutter release button and various settingswitches, including a power switch, outputs an operation signalcorresponding to a specific operation to the body control unit 27.

In addition, the body control unit 27 includes the first bodycommunication unit 28 and the second body communication unit 29. As willbe explained later, the first body communication unit 28 is engaged incommand data communication with the first lens communication unit 38 viathe body-side connection unit 202 and the lens-side connection unit 302.The second body communication unit 29 is engaged in hotlinecommunication with the second lens communication unit 39 via thebody-side connection unit 202 and the lens-side connection unit 302.

Next, command data communication will be explained. The first lenscommunication unit 38 and the first body communication unit 28 carry outfull duplex communication via the individual terminals disposed in thelens-side connection unit 302 and the body-side connection unit 202. Aswill be explained later in reference to FIG. 2, the first lenscommunication unit 38 and the first body communication unit 28 exchangefour different types of signals such as an RDY signal, a CLK signal, aDATAB signal and a DATAL signal.

The RDY signal indicates whether or not the first lens communicationunit 38 is in a communication-enabled state and is switched to highlevel (H level) or to low level (L level) by the first lenscommunication unit 38. The RDY signal is a signal transmitted (output)to the first body communication unit 28. The CLK signal is a clocksignal originating on the camera body-side, which is transmitted fromthe first body communication unit 28 to the first lens communicationunit 38. The DATAB signal is a data signal transmitted from the firstbody communication unit 28 to the first lens communication unit 38. TheDATAL signal is a data signal transmitted from the first lenscommunication unit 38 to the first body communication unit 28.

Next, information (commands, data) transmitted/received through commanddata communication will be explained. Data pertaining to the opticalcharacteristics (maximum F number, aberration and the like) of thephotographic optical system 31, data pertaining to the infinity positionand the close-up position of the focus lens, the lens-side generationinformation, information indicating response contents (response data)including, for instance, the execution status of initialization,executed in response to an initialization command issued by the camerabody 2 as will be explained later, or the like, is transmitted in theDATAL signal from the interchangeable lens 3 to the camera body 2.Generation information indicating the communication specifications to beapplied to hotline communication, which will be explained later, acontrol command providing an instruction for drive of the focus lens,the anti-vibration lens or the zoom lens in the photographic opticalsystem 31, drive of the aperture stop 32 or lens initialization, dataindicating control contents (control data) or the like, for instance, istransmitted in the DATAB signal from the camera body 2 to theinterchangeable lens 3.

FIG. 2 is a diagram in reference to which command data communicationcarried out in the image capturing device in the first embodiment willbe explained. The schematic chart presented in FIG. 2 indicates anexample of timing with which command data communication may be carriedout by the lens control unit 37 and the body control unit 27 via thefirst lens communication unit 38 and the first body communication unit28. The first lens communication unit 38 transmits/receives the RDYsignal, the CLK signal, the DATAB signal and the DATAL signal to/fromthe first body communication unit 28.

The signal level assumed for the RDY signal indicates whether or not thefirst lens communication unit 38 is in a communication-enabled state.When the first lens communication unit 38 is in a state in which it isable to communicate with the first body communication unit 28, the lenscontrol unit 37 sets the RDY signal to low level (L level, e.g., theground voltage or a reference voltage). If the first lens communicationunit 38 is in a state in which it is not able to communicate with thefirst body communication unit 28, the lens control unit 37 sets the RDYsignal to high level (H level, e.g., the source voltage). The first bodycommunication unit 28 detects the signal level of the RDY signal and thebody control unit 27 makes a decision as to whether or not the firstlens communication unit 38 is in a communication-enabled state.

At a time point t1 at which the RDY signal is at low level (L level),the first body communication unit 28 outputs (transmits) a clock signal(CLK signal) to the first lens communication unit 38. In other words,the first body communication unit 28 alternately switches the signallevel of the CLK signal, which has been sustained at a predeterminedvoltage (e.g., high level, the source voltage) up to the time point t1,between high level and low level (e.g., the ground voltage or areference voltage) over a predetermined cycle at the time point t1 andbeyond. In addition, during a period of time elapsing between the timepoint t1 and a time point t2, the first body communication unit 28transmits a command packet 41 in a DATAB signal in synchronization witha rise or a fall of the CLK signal.

It is to be noted that when the RDY signal is at high level (H level),the first lens communication unit 38 is not receptive to communication,and in this state, the first body communication unit 28 does nottransmit a command or data to the first lens communication unit 38. Inthis situation, the first body communication unit 28 sustains the signallevels of the CLK signal and the DATAB signal at a predetermined fixedvoltage (e.g., high level).

The lens control unit 37 verifies the contents of the command packet 41input thereto from the first body communication unit 28 through, forinstance, checksum processing or the like and makes a decision as towhether or not the command packet 41 has been received normally. Ifreception of the command packet 41 at the first lens communication unit38 is normal, the lens control unit 37 sets the RDY signal to high levelat a time point t3. The lens control unit 37 also executes firstprocessing 51 in correspondence to the contents of the command packet41. Once the first processing 51 is completed, the lens control unit 37sets the RDY signal to low level at a time point t4. It is to be notedthat if reception of the command packet 41 at the first lenscommunication unit 38 was not normal, the lens control unit 37 notifiesthe first body communication unit 38 that normal reception of thecommand packet 41 has not occurred by sustaining the RDY signal at lowlevel.

Upon detecting that the RDY signal has shifted from high level to lowlevel, the first body communication unit 28 resumes the output of theCLK signal at a time point t5. In addition, during a period of timeelapsing between the time point t5 and a time point t6, the first bodycommunication unit 28 transmits a data packet 42 in a DATAB signal insynchronization with a rise or a fall of the CLK signal. During the sametime period elapsing between the time point t5 and the time point t6,the first lens communication unit 38 transmits a data packet 43 in aDATAL signal in synchronization with a rise or a fall of the CLK signalinput thereto from the first body communication unit 28.

As the data packet 42 from the first body communication unit 28 isreceived in a normal manner at the first lens communication unit 38, thelens control unit 37 sets the RDY signal to high level at a time pointt7. The lens control unit 37 executes second processing 52 incorrespondence to the contents of the data packet 42. Once the secondprocessing 52 is completed, the lens control unit 37 sets the RDY signalto low level at a time point t8.

The contents of the command packet 41 and the data packet 42 output fromthe first body communication unit 28 as described above may be, forinstance, a request for initialization of the interchangeable lens 3, arequest for specific data, a drive instruction for a drive target member(e.g., the focus lens, the aperture stop or the like) in thephotographic optical system 31, a start instruction for the second lenscommunication unit 39 to start hotline communication and the like. Thelens control unit 37 executes processing for generating the specificdata having been requested, processing for driving the drive targetmember, or the like, as the first processing 51 or the second processing52. The lens control unit 37 transmits, for instance, flag dataindicating that initialization of the interchangeable lens 3 has beencompleted, data indicating the optical characteristics of theinterchangeable lens 3, data indicating that the drive of the drivetarget member has been completed as instructed, or the like in the datapacket 43.

Next, hotline communication will be explained in detail. The second lenscommunication unit 39 and the second body communication unit 29 shown inFIG. 1 are engaged in unidirectional communication from theinterchangeable lens 3 to the camera body 2 via individual terminals inthe lens-side connection unit 302 and the body-side connection unit 202.The second lens communication unit 39 transmits two types of signals,such as an HCLK signal and an HDATA signal to the second bodycommunication unit 29.

The HCLK signal is a clock signal originating on the interchangeablelens-side, transmitted from the second lens communication unit 39 to thesecond body communication unit 29. The HDATA signal, which is a datasignal transmitted from the second lens communication unit 39 to thesecond body communication unit 29, carries information pertaining to thelens position of the focus lens, the zoom lens or the anti-vibrationlens explained earlier or information pertaining to the opening diameterof the aperture stop 32. The second lens communication unit 39 transmitsthe HDATA signal to the second body communication unit 29 insynchronization with a cyclical rise or fall of the HCLK signal. Inother words, the second lens communication unit 39 and the second bodycommunication unit 29 are engaged in unidirectional communicationthrough which a clock signal and a data signal are transmitted from thesecond lens communication unit 39 to the second body communication unit29.

It is to be noted that the cycle of the CLK signal used in command datacommunication either substantially matches or is shorter than the cycleof the HCLK signal used in hotline communication. The frequency of theCLK signal output from the camera body 2 to the interchangeable lens 3may be, for instance, 8 MHz, whereas the frequency of the HCLK signaloutput from the interchangeable lens 3 to the camera body 2 may be, forinstance, 2.5 MHz to 8 MHz.

Next, the electrical connections at the lens-side connection unit 302and the body-side connection unit 202 will be explained. FIG. 3 is adiagram schematically illustrating the electric connections achieved atthe lens-side connection unit 302 and the body-side connection unit 202.The body-side connection unit 202 includes an LDET (B) terminal, a VBAT(B) terminal, a PGND (B) terminal, a V33 (B) terminal, a GND (B)terminal, a RDY (B) terminal, a DATAB (B) terminal, a CLK (B) terminal,a DATAL (B) terminal, an HCLK (B) terminal and an HDATA (B) terminal.The 11 body-side terminals will be collectively referred to as abody-side terminal group.

The LDET (B) terminal is a terminal used to sense whether or not theinterchangeable lens 3 is mounted. The LDET (B) terminal is connected tothe body control unit 27 via a resistor R2. A source V33 supplied fromthe power supply unit 26 is connected, via a resistor R1, between theresistor R2 and the body control unit 27, thereby pulling up the LDET(B) terminal.

The VBAT (B) terminal, the PGND (B) terminal, the V33 (B) terminal andthe GND (B) terminal are camera body-side source system terminals, whichare connected to the power supply unit 26. In FIG. 3, the directionalong which electric power is supplied is indicated by arrows. The VBAT(B) terminal is a terminal used to provide electric power (provide thesource voltage) to the drive system of the interchangeable lens 3. Thelens drive unit 33 in the interchangeable lens 3 is driven with electricpower provided via the VBAT (B) terminal. The voltage applied by thepower supply unit 26 to the VBAT (B) terminal is, at most, approximately10 V. The PGND (B) terminal is a ground terminal corresponding to theVBAT (B) terminal, which assumes a ground potential (ground) for thedrive system source voltage supplied via the VBAT (B) terminal.

The V33 (B) terminal is a terminal used to provide electric power(provide the source voltage) to the circuit system in theinterchangeable lens 3. The lens control unit 37 and the like areengaged in operation with the electric power provided from the powersupply unit 26 via the V33 (B) terminal. Components such as the lenscontrol unit 37 can be engaged in operation at a lower voltage and asmaller current than the lens drive unit 33. The voltage applied by thepower supply unit 26 to the V33 (B) terminal is, at most, approximately3.3 V. The GND (B) terminal is a ground terminal corresponding to theV33 (B) terminal and assumes a ground potential (ground) for the sourcevoltage supplied to the circuit system via the V33 (B) terminal.

The RDY (B) terminal, the DATAB (B) terminal, the CLK (B) terminal, theDATAL (B) terminal, the HCLK (B) terminal and the HDATA (B) terminal arecommunication system terminals connected to the body control unit 27 andare used to transmit/receive the RDY signal, the DATAB signal, the CLKsignal, the DATAL signal, the HCLK signal and the HDATA signal to/fromthe corresponding RDY (L) terminal, DATAB (L) terminal, CLK (L)terminal, DATAL (L) terminal, HCLK (L) terminal and HDATA (L) terminalto be explained later. The RDY (B) terminal, the DATAB (B) terminal, theCLK (B) terminal and the DATAL (B) terminal are connected to the firstbody communication unit 28 in the body control unit 27 and are used incommand data communication as has been explained earlier. In addition,the HCLK (B) terminal and the HDATA (B) terminal are connected to thesecond body communication unit 29 and are used in hotline communicationas has been explained earlier. In FIG. 3, flows of signals are indicatedwith arrows. The potential at the RDY (B) terminal indicates whether ornot the interchangeable lens 3 is able to carry out command datacommunication. The DATAB (B) terminal is a terminal through which asignal is output to the interchangeable lens 3. The CLK (B) terminal isa terminal through which a clock signal originating on the camerabody-side is output to the interchangeable lens 3.

The DATAL (B) terminal is a terminal through which a data signal fromthe interchangeable lens 3 is input.

The HCLK (B) terminal is a terminal through which a clock signaloriginating on the interchangeable lens-side is input from theinterchangeable lens 3. The HDATA (B) terminal is a terminal throughwhich a data signal from the interchangeable lens 3 is input.

The lens-side connection unit 302 includes the LDET (L) terminal, theVBAT (L) terminal, the PGND (L) terminal, the V33 (L) terminal, the GND(L) terminal, the RDY(L) terminal, the DATAB (L) terminal, the CLK(L)terminal, the DATAL (L) terminal, the HCLK (L) terminal and the HDATA(L) terminal. These 11 lens-side terminals will be collectively referredto as a lens-side terminal group.

As the interchangeable lens 3 is mounted at the camera body 2, thebody-side terminals and the lens-side terminals become electricallyconnected with each other, as indicated with the dotted lines in FIG. 3.More specifically, the LDET (L) terminal is connected to the LDET (B)terminal, the VBAT (L) terminal is connected to the VBAT (B) terminal,the PGND (L) terminal is connected to the PGND (B) terminal, the V33 (L)terminal is connected to the V33 (B) terminal, the GND (L) terminal isconnected to the GND (B) terminal, the RDY (L) terminal is connected tothe RDY(B) terminal, the DATAB (L) terminal is connected to the DATAB(B) terminal, the CLK (L) terminal is connected to the CLK(B) terminal,the DATAL (L) terminal is connected to the DATAL (B) terminal, the HCLK(L) terminal is connected to the HCLK (B) terminal and the HDATA (L)terminal is connected to the HDATA (B) terminal. The roles of theindividual lens-side terminals correspond to the roles of the body-sideterminals to which they are connected.

The LDET (L) terminal is grounded via a resistor R3. As the LDET (L)terminal comes into contact with the LDET (B) terminal, the potential atthe LDET (B) terminal is pulled down. The VBAT (L) terminal and the PGND(L) terminal are connected to the lens drive unit 33 and the aperturedrive unit 35 via the lens control unit 37. A capacitor C1, which isgenerally referred to as a bypass capacitor, is connected between theVBAT (L) terminal and the PGND (L) terminal. The V33 (L) terminal andthe GND (L) terminal are connected to the lens control unit 37. A bypasscapacitor C2 is connected between the V33 (L) terminal and the GND (L)terminal. The RDY (L) terminal, the DATAB (L) terminal, the CLK (L)terminal, the DATAL (L) terminal, the HCLK (L) terminal and the HDATA(L) terminal are each connected to the lens control unit 37. The RDY (L)terminal, the DATAB (L) terminal, the CLK (L) terminal and the DATAL (L)terminal are connected to the first lens communication unit 38 in thelens control unit 37 and are used in command data communication as hasbeen explained earlier. In addition, the HCLK (L) terminal and the HDATA(L) terminal are connected to the second lens communication unit 39 andare used in hotline communication as has been explained earlier.

Communication, through which control contents (control data) from thebody control unit 27 and response contents (response data) from the lenscontrol unit 37 are concurrently transmitted/received after a controlcommand from the body control unit 27 is transmitted to the lens controlunit 37 at the interchangeable lens 3, is referred to as command datacommunication. The command data communication is full duplexcommunication. The command data communication is carried out throughdigital data communication executed by using the RDY(B) terminal, theRDY (L) terminal, the DATAB (B) terminal, the DATAB (L) terminal, theCLK (B) terminal, the CLK (L) terminal, the DATAL (B) terminal and theDATAL (L) terminal via the first body communication unit 28 and thefirst lens communication unit 38.

The body control unit 27 transmits various control commands and controlcontents to the interchangeable lens 3 and receives response contentsfrom the interchangeable lens 3 so as to transmit/receive various typesof information to/from the interchangeable lens 3 through command datacommunication carried out via the first body communication unit 28 andthe first lens communication unit 38. A control command transmittedthrough this communication may be, for instance, a lens informationtransmission command. The various types of information received from theinterchangeable lens 3 may be, for instance, model informationpertaining to the interchangeable lens 3, information indicating theoptical characteristics such as the focal length of the image capturingoptical system 31 and the like. Various types of information transmittedto the interchangeable lens 3 may be, for instance, control contentssuch as a lens drive quantity, model information pertaining to thecamera body 2 and the like. It is to be noted that control commands alsoinclude a drive command for the focus lens (not shown). Through commanddata communication, the lens control unit 37 receives various controlcommands and various types of information from the body control unit 27and transmits various types of information to the body control unit 27.

FIG. 4A is a schematic illustration of the mount at the camera body 2,viewed from the side where the interchangeable lens 3 is located. Thebody-side mount unit 201 includes an annular reference surface having aconstant width. The body-side mount unit 201 further includes abody-side first claw or tab portion 129 a, a body-side second clawportion 129 b, a body-side third claw portion 129 c and a body-sidefourth claw portion 129 d. In the following description, these four clawportions may be generically referred to as body-side claw portions 129.

The body-side claw portions 129 are disposed at positions set apart fromone another along the circular opening of the body-side mount unit 201.As FIG. 4A illustrates, the body-side first claw portion 129 a isdisposed at an upper right position, the body-side second claw portion129 b is disposed at an upper left position, the body-side third clawportion 129 c is disposed at a lower left position and the body-sidefourth claw portion 129 d is disposed at a lower right position.

The body-side first claw portion 129 a through the body-side fourth clawportion 129 d have lengths, measured along the circumferentialdirection, that are different from one another. In more specific terms,the body-side first claw portion 129 a has the greatest length, thebody-side third claw portion 129 c has the second greatest length, thebody-side fourth claw portion 129 d has the third greatest length andthe body-side second claw portion 129 b has the smallest length.

The body-side claw portions 129 project out from the body-side mountunit 201 toward the center of the opening, and the circumferential areaalong the opening includes areas where the body-side claw portions 129are present and areas where no body-side claw portion 129 is present. Inthe following description, a space 140 a located between the body-sidefirst claw portion 129 a and the body-side fourth claw portion 129 d onthe circumference of the opening of the body-side mount unit 201 will bereferred to as a body-side first through portion 140 a. Likewise, aspace 140 b located between the body-side first claw portion 129 a andthe body-side second claw portion 129 b will be referred to as abody-side second through portion 140 b, a space 140 c located betweenthe body-side second claw portion 129 b and the body-side third clawportion 129 c will be referred to as a body-side third through portion140 c and a space 140 d located between the body-side third claw portion129 c and the body-side fourth claw portion 129 d will be referred to asa body-side fourth through portion 140 d. These four body-side throughportions will be generically referred to as body-side through portions140.

The body-side connection unit 202 is disposed on the inner side alongthe opening of the body-side mount unit 201. The body-side connectionunit 202 assumes a circular arc shape corresponding to the shape of theannular body-side mount unit 201. It is preferable that the body-sideconnection unit 202 be disposed at an upper part in the opening of thebody-side mount unit 201 so as to range along the opening of thebody-side mount unit 201 at the top center position as shown in FIG. 4A.The body-side connection unit 202 includes a plurality of body-sideterminals as has been explained earlier. The plurality of body-sideterminals are disposed in the body-side connection unit 202 in a singleline so as to form a circular arc on the inner side of the body-sidemount unit 201. The plurality of body-side terminals are 11 terminals,i.e., HDATA (B), HCLK (B), DATAL (B), CLK(B), DATAB (B), RDY (B), GND(B), V33 (B), PGND (B) VBAT (B) and LDET (B), disposed in this orderstarting from the right side and the LDET (B) terminal located at thefurthest left position, as shown in FIG. 4A. The terminals in thebody-side terminal group are each constituted with an electricallyconductive pin. The body-side terminal group is pressed along the −Zdirection (see FIG. 1) by a spring or the like (not shown). The −Zdirection is a direction running toward the interchangeable lens 3 to bemounted at the camera body 2, i.e., running toward the subject.

The body-side mount unit 201 includes a hole through which a lock pin142 is inserted. The hole through which the lock pin 142 is inserted isformed at an upper right position relative to the body-side fourth clawportion 129 d. In other words, the hole for the lock pin 142 is disposedon the annular reference surface of the body-side mount unit 201, at aposition between the area along the opening of the body-side mount 201the inner side of which the body-side fourth claw portion 129 d ispresent and the area along the opening the inner side of which thebody-side first claw portion 129 a is present. The lock pin 142 ispressed along the −Z direction (see FIG. 1) by a spring or the like (notshown).

FIG. 4B is a schematic illustration of the mount at the camera body 2without the body-side mount unit 201, viewed from the side where theinterchangeable lens 3 is located. A first plate spring 141 a isdisposed at a position (on the back side of the body-side first clawportion 129 a which is the +Z direction) corresponding to the body-sidefirst claw portion 129 a. Likewise, a second plate spring 141 b isdisposed at a position (on the back side of the body-side second clawportion 129 b) corresponding to the body-side second claw portion 129 b,a third plate spring 141 c is disposed at a position (on the back sideof the body-side third claw portion 129 c) corresponding to thebody-side third claw portion 129 c and a fourth plate spring 141 d isdisposed at a position (on the back side of the body-side fourth clawportion 129 d) corresponding to the body-side fourth claw portion 129 d.In the following description, these four plate springs will begenerically referred to as plate springs 141. Lens-side claw portions,to be described later, are pressed along the +Z direction (toward thecamera body 2) via the plate springs 141.

FIG. 5 is a schematic illustration of the mount at the interchangeablelens 3, viewed from the side where the camera body 2 is located. Theinterchangeable lens 3 includes the lens-side mount unit 301 and thelens-side connection unit 302 having been described in reference toFIG. 1. The lens-side mount unit 301 includes an annular referencesurface assuming a constant width. As the interchangeable lens 3 ismounted at the camera body 2, the annular reference surface of thelens-side mount unit 301 comes into contact with the annular referencesurface of the body-side mount unit 201 mentioned earlier. The lens-sidemount unit 301 further includes a cylindrical portion disposed at theinner circumference thereof, which ranges along the optical axis. Thelens-side mount unit 301 includes a lens-side first claw portion 139 a,a lens-side second claw portion 139 b, a lens-side third claw portion139 c and a lens-side fourth claw portion 139 d, disposed at positionsset apart from one another along the outer circumference of thecylindrical portion. In the following description, these four clawportions will be generically referred to as lens-side claw portions 139.

The lens-side claw portions 139 are disposed so as to project outwardfrom the outer circumference of the cylindrical portion of the lens-sidemount unit 301 (along a radial direction originating at the optical axisL). As shown in FIG. 5, the lens-side first claw portion 139 a isdisposed at an upper left position, the lens-side second claw portion139 b is disposed at an upper right position, the lens-side third clawportion 139 c is disposed at a lower right position and the lens-sidefourth claw portion 139 d is disposed at a lower left position. On theside to the rear relative to the lens-side claw portions 139 (toward thereference surface of the lens-side mount unit 301), spaces into whichthe corresponding body-side claw portions 129 are inserted as theinterchangeable lens 3 is mounted at the camera body 2 are present.

The lens-side connection unit 302 is disposed at the inner side of theopening of the lens-side mount unit 301. The lens-side connection unit302 assumes a circular arc shape corresponding to the shape of theannular lens-side mount unit 301. It is preferable that the lens-sideconnection unit 302 be disposed at an upper part in the opening of thelens-side mount unit 301 along the opening of the lens-side mount unit301 so as to be disposed at the top center position, as shown in FIG. 5.The lens-side connection unit 302 includes a plurality of lens-sideterminals as has been explained earlier. The plurality of lens-sideterminals are disposed in the lens-side connection unit 302 in a singlerow so as to form a circular arc on the inner side of the lens-sidemount unit 301. The plurality of lens-side terminals, i.e., the 11terminals; LDET (L), VBAT (L), PGND (L), V33 (L), GND (L), RDY (L),DATAB (L), CLK(L), DATAL (L), HCLK (L) and HDATA (L), are disposed inthis order starting from the right side, as shown in FIG. 5. Theterminals in the lens-side terminal group are each disposed so that itselectrically conductive contact surface is exposed toward the +Zdirection (see FIG. 1). The +Z direction is a direction along which thesubject light having passed through the photographic optical system 31advances toward the image sensor 21.

The lens-side mount unit 301 includes a lock pin receptacle portion 143.The lock pin receptacle portion 143 is disposed at an upper leftposition relative to the lens-side fourth claw portion 139 d, as shownin FIG. 5. In other words, the lock pin receptacle portion 143 isdisposed at a position located between an area of the lens-side mountunit 301 corresponding to the lens-side first claw portion 139 a and anarea of the lens-side mount unit 301 corresponding to the lens-sidefourth claw portion 139 d. The lock pin receptacle portion 143 is agroove in which the lock pin 142 is housed when the interchangeable lens3 is mounted at the camera body 2. This groove ranges from the referencesurface of the lens-side mount unit 301 along the −Z direction (see FIG.1).

As the interchangeable lens 3 is mounted at the camera body 2, theplurality of body-side terminals come into physical contact with theplurality of corresponding lens-side terminals. Through this contact,the plurality of body-side terminals and the plurality of lens-sideterminals become electrically connected. Namely, the plurality ofbody-side terminals and the plurality of lens-side terminals becomeelectrically continuous.

Mounting the Interchangeable Lens

The method adopted when mounting the interchangeable lens 3 at thecamera body 2 will be explained next. The interchangeable lens 3 ismounted at the camera body 2 by first placing the body-side mount unit201 and the lens-side mount unit 301 so that they face opposite eachother, positioning the lens-side first claw portion 139 a at thebody-side first through portion 140 a, the lens-side second claw portion139 b at the body-side second through portion 140 b, the lens-side thirdclaw portion 139 c at the body-side third through portion 140 c and thelens-side fourth claw portion 139 d at the body-side fourth throughportion 140 d. The lens-side first claw portion 139 a is inserted intothe body-side first through portion 140 a, the lens-side second clawportion 139 b is inserted into the body-side second through portion 140b, the lens-side third claw portion 139 c is inserted into the body-sidethird through portion 140 c and the lens-side fourth claw portion 139 dis inserted into the body-side fourth through portion 140 d. At thistime, the LDET (L) terminal, the VBAT (L) terminal, the PGND (L)terminal and the V33 (L) terminal respectively come into contact withthe CLK (B) terminal, the DATAL (B) terminal, the HCLK (B) terminal andthe HDATA (B) terminal.

In the state described above, the interchangeable lens 3 is rotatedalong a mounting direction 144, as indicated in FIG. 4A and FIG. 5. Inother words, the body-side first claw portion 129 a moves into the spacelocated on the back side of the lens-side first claw portion 139 a, thebody-side second claw portion 129 b moves into the space located on theback side of the lens-side second claw portion 139 b, the body-sidethird claw portion 129 c moves into the space located on the back sideof the lens-side third claw portion 139 c and the body-side fourth clawportion 129 d moves into the space located on the back side of thelens-side fourth claw portion 139 d. At this time, the plurality oflens-side terminals each sequentially come into contact with a pluralityof body-side terminals. It is to be noted that the camera body 2,instead of the interchangeable lens 3, may be rotated along a directionopposite from the mounting direction 144 indicated in FIG. 4A and FIG.5.

As the lens-side claw portions 139 are inserted in the correspondingbody-side through portions 140 and the interchangeable lens 3 is rotatedalong the mounting direction 144, the LDET (L) terminal, for instance,comes into contact, in sequence, with the CLK(B) terminal, the DATAB (B)terminal, the RDY (B) terminal, the GND (B) terminal, the V33 (B)terminal, the PGND (B) terminal, the VBAT (B) terminal and the LDET (B)terminal. The VBAT (L) terminal comes into contact, in sequence, withthe DATAL (B) terminal, the CLK (B) terminal, the DATAB (B) terminal,the RDY (B) terminal, the GND (B) terminal, the V33 (B) terminal, thePGND (B) terminal and the VBAT (B) terminal. The PGND (L) terminal comesinto contact, in sequence, with the HCLK (B) terminal, the DATAL (B)terminal, the CLK (B) terminal, the DATAB (B) terminal, the RDY(B)terminal, the GND (B) terminal, the V33 (B) terminal and the PGND (B)terminal. The V33 (L) terminal comes into contact, in sequence, with theHDATA (B) terminal, the HCLK (B) terminal, the DATAL (B) terminal, theCLK (B) terminal, the DATAB (B) terminal, the RDY (B) terminal, the GND(B) terminal and the V33 (B) terminal. The GND (L) terminal comes intocontact, in sequence, with the HDATA (B) terminal, the HCLK (B)terminal, the DATAL (B) terminal, the CLK (B) terminal, the DATAB (B)terminal, the RDY (B) terminal and the GND(B) terminal.

The RDY (L) terminal comes into contact, in sequence, with the HDATA (B)terminal, the HCLK (B) terminal, the DATAL (B) terminal, the CLK (B)terminal, the DATAB (B) terminal and the RDY (B) terminal. The DATAB (L)terminal comes into contact, in sequence, with the HDATA (B) terminal,the HCLK (B) terminal, the DATAL (B) terminal, the CLK (B) terminal andthe DATAB (B) terminal. The CLK (L) terminal comes into contact, insequence, with the HDATA (B) terminal, the HCLK (B) terminal, the DATAL(B) terminal and the CLK (B) terminal. The DATAL (L) terminal comes intocontact, in sequence, with the HDATA (B) terminal, the HCLK (B) terminaland the DATAL (B) terminal. The HCLK (L) terminal comes into contact, insequence, with the HDATA (B) terminal and the HCLK (B) terminal.

As the interchangeable lens 3 is rotated by a predetermined anglerelative to the camera body 2, it reaches a mount-complete position. Atthe mount-complete position, each body-side claw portion 129 facesopposite the corresponding lens-side claw portion 139 in the directionof the optical axis and the lock pin 142, pressed along the −Z directionin FIG. 1, moves into the lock pin receptacle portion 143. Once the lockpin 142 moves into the lock pin receptacle portion 143, theinterchangeable lens 3 can no longer be rotated and thus cannot bedisengaged from the camera body 2. Namely, once the body-side clawportions 129 and the lens-side claw portions 139 reach the predefinedmount-complete positions, the positions of the body-side mount unit 201and the lens-side mount unit 301 relative to each other become fixed.The lens-side claw portions 139 are pressed toward the body-side (+Zdirection in FIG. 1) by the plate springs 141. As a result, theplurality of lens-side terminals each come into contact with thecorresponding body-side terminal among the plurality of body-sideterminals and become electrically connected.

In the following description, the state in which the body-side clawportions 129 and the lens-side claw portions 139 have reached thepredetermined mount-complete positions will be referred to as a mountcomplete state. A state in which the lens-side claw portions 139, havingbeen inserted in the body-side through portions 140, are in the processof moving toward the mount-complete position or a state in which theyare moving from the mount-complete position toward the insertionposition will be referred to as a mount-incomplete state.

In a mount-incomplete state, the signal level at the LDET (B) terminalis pulled up to high level. When the signal level at the LDET (B)terminal is detected to be high level, the body control unit 27determines that the interchangeable lens 3 is not mounted. When theinterchangeable lens 3 is not mounted, the body control unit 27 does notallow the power supply unit 26 to provide electric power to the VBAT (B)terminal and the V33 (B) terminal.

In a mount-complete state, the signal level at the LDET (B) terminal ispulled down to low level, as has been explained (FIG. 3). Once thesignal level at the LDET (B) terminal is detected to be low level, thebody control unit 27 determines that the interchangeable lens 3 has beenmounted. In addition, in the mount-complete state, the lock pin 142 willhave moved into the lock pin receptacle portion 143, thereby turning ona lock pin detection switch (not shown) that interlocks with the lockpin 142. Upon detecting that the signal level at the LDET (B) terminalhas shifted to low level and that the lock pin detection switch has beenturned on, the body control unit 27 engages the power supply unit 26 tostart providing electric power to the V33 (B) terminal, i.e., to supplya circuit system source voltage. It is to be noted that the camera body2 does not need to include a lock pin detections switch. At a camerabody 2 that does not include a lock pin detection switch, the powersupply unit 26 will start supplying electric power to the V33 (B)terminal upon detecting that the signal level at the LDET (B) terminalhas shifted to low level.

Once the power supply to the V33 (B) terminal starts, the source voltageis supplied to the lens control unit 37 at the interchangeable lens 3through the V33 (L) terminal, and the lens control unit 37 thus startsoperation. The lens control unit 37 having become engaged in operationpermits initial communication through command data communication to becarried out with the body control unit 27. Once the lens control unit 37permits initial communication, the body control unit 27 starts initialcommunication. Information exchanged in the initial communicationincludes a signal requesting power supply to the VBAT (L) terminal,transmitted by the lens control unit 37. In response to the signalrequesting power supply to the VBAT (L) terminal, transmitted from thelens control unit 37 to the body control unit 27, the body control unit27 provides a source voltage to the VBAT (B) terminal and initializationprocessing is executed for the camera body 2 and the interchangeablelens 3. In the initialization processing, information required in orderto execute various operations in the camera 1, such as photographingoperation and focus adjustment operation, is exchanged between thecamera body 2 and the interchangeable lens 3 and the interchangeablelens is moved to a reference position.

As the user presses down a lock-release button (not shown) at the camerabody 2 in a mount-complete state, the lock pin 142 moves out of the lockpin receptacle portion 143. As a result, it becomes possible to alterthe positions of the body-side mount unit 201 and the lens-side mountunit 301 relative to each other. Once the user presses down thelock-release button (not shown), the lock pin detection switch,interlocking with the lock-release button, is turned off and the bodycontrol unit 27 controls the power supply unit 26 so as to stop thepower supply to the VBAT (B) terminal and the V33 (B) terminal. As theinterchangeable lens 3 is rotated in this state along the directionopposite from the mounting direction 144 indicated in FIG. 4A and FIG.5, the plurality of lens-side terminals each come into contact with aplurality of body-side terminals in a sequence opposite from thatdescribed earlier.

It is to be noted that the power supply cessation does not need tointerlock with a lock-release button operation. Namely, the body controlunit 27 may control the power supply unit 26 to stop the power supply tothe VBAT (B) terminal and the V33 (B) terminal upon sensing that thesignal level at the LDET (B) terminal, no longer in contact with theLDET (L) terminal as the interchangeable lens 3 is rotated along thedirection opposite from the mounting direction 144, has shifted from lowlevel to high level. In this case, the number of required parts in thecamera 1 can be reduced. As an alternative, the power supply unit 26 maystop power supply to the VBAT (B) terminal and the V33 (B) terminal uponsensing that the lock-release button has been pressed down and also thatthe signal level at the LDET (B) terminal has shifted from low level tohigh level. As a further alternative, the body control unit 27 maycontrol the power supply unit 26 to stop power supply to the VBAT (B)terminal and the V33 (B) terminal upon sensing either that thelock-release button has been pressed down or that the signal level atthe LDET (B) terminal has shifted from low level to high level.

As described above, while the interchangeable lens is being mounted atthe camera body or being dismounted from the camera body (in amount-incomplete state) the lens-side terminals each come into contactwith body-side terminals other than the corresponding terminal withwhich it comes into contact in a mount-complete state. It is desirablethat the lens-side terminals and the body-side terminals be disposedwith a positional arrangement that minimizes any problems that may arisefrom such contact occurring during the mounting process and thedismounting process.

In the embodiment, the LDET (B) terminal among the plurality ofbody-side terminals is disposed at the leading end along the lensmounting direction (indicated by the arrow 144 in FIG. 4A). In otherwords, the LDET (B) terminal is disposed at the position furthest to theleft among the terminals in the body-side terminal group in FIG. 4A, asexplained earlier. The LDET (L) terminal among the plurality oflens-side terminals is likewise disposed at the leading end along thelens mounting direction (indicated by the arrow 144 in FIG. 5). Thismeans that the LDET (L) terminal is disposed at the position furthest tothe right among the terminals in the lens-side terminal group in FIG. 5as described above. Thus, the LDET (B) terminal does not come intocontact with any lens-side terminal other than the LDET (L) terminalbefore the interchangeable lens is completely mounted. For this reason,the signal level at the LDET (B) terminal does not erroneously shift tolow level during the process of mounting the interchangeable lens andconsequently, the lens is not erroneously recognized as mounted.

In the embodiment, the VBAT (B) terminal is disposed next to the LDET(B) terminal, i.e., at a second position from the leading end along themounting direction. The VBAT (L) terminal is disposed next to the LDET(L) terminal, i.e., at a second position from the leading end along themounting direction. Such a positional arrangement is adopted in order tominimize the number of lens-side terminals with which the VBAT (B)terminal on the camera body side comes into contact during the lensmounting process. The voltage applied to the VBAT (B) terminal is higherthan the voltage applied to the other terminals, and thus, if the VBAT(B) terminal comes into contact with a terminal other than the VBAT (L)terminal under a condition in which a high voltage is erroneouslyapplied to the VBAT (B) terminal due to a malfunction in the camera 1 orthe like, the high voltage may place an unexpected load on the electriccircuit within the interchangeable lens. In the embodiment, The VBAT (B)terminal is disposed at a position next to the LDET (B) terminal andthus only the LDET (L) terminal among the plurality of lens-sideterminals comes into contact with the VBAT (B) terminal in amount-incomplete state while mounting the interchangeable lens 3. TheLDET (L) terminal is grounded via a resistor (the resistor R3 in FIG. 3)and for this reason, even if a high voltage is applied thereto from theVBAT (B) terminal, the camera 1 will remain unaffected.

In the embodiment, the PGND (B) terminal is disposed next to the VBAT(B) terminal, i.e., at a third position from the leading end along themounting direction. The PGND (L) terminal is disposed next to the VBAT(L) terminal, i.e., at a third position from the leading end along themounting direction. The high voltage supplied through the VBAT (B)terminal is accumulated as an electric charge in the capacitor C1connected to the VBAT (L) terminal. As the interchangeable lens 3 isrotated along the dismounting direction (the direction opposite from themounting direction 144), the VBAT (L) terminal first comes into contactwith the PGND (B) terminal. The electric charge accumulated in thecapacitor C1 is promptly discharged through the PGND (B) terminal, whichis a ground terminal, without affecting the other circuits in the camera1.

In the embodiment, the V33 (B) terminal is disposed next to the PGND (B)terminal, i.e., at a fourth position from the leading end along themounting direction, and the GND (B) terminal is disposed next to the V33(B) terminal, i.e. at a fifth position from the leading end. The V33 (L)terminal is disposed next to the PGND (L) terminal, i.e., at a fourthposition from the leading end along the mounting direction, and the GND(L) terminal is disposed next to the V33 (L) terminal, i.e. at a fifthposition from the leading end. The voltage supplied through the V33 (B)terminal is accumulated as an electric charge in the capacitor C2connected to the V33 (L) terminal. As the interchangeable lens 3 isrotated along the dismounting direction (the direction opposite from themounting direction 144), the V33 (L) terminal first comes into contactwith the GND (B) terminal. The electric charge accumulated in thecapacitor C2 is promptly discharged through the GND (B) terminal, whichis a ground terminal, without affecting the other circuits in the camera1.

The RDY (B) terminal is disposed next to the GND (B) terminal, i.e., ata sixth position from the leading end, the DATAB (B) terminal isdisposed next to the RDY (B) terminal, i.e., at a seventh position fromthe leading end, the CLK (B) terminal is disposed next to the DATAB (B)terminal, i.e., at an eighth position from the leading end, the DATAL(B) terminal is disposed next to the CLK (B) terminal, i.e., at a ninthposition from the leading end, the HCLK (B) terminal is disposed next tothe DATAL (B) terminal, i.e., at a 10th position from the leading endand the HDATA (B) terminal is disposed next to the HCLK (B) terminal,i.e., at the trailing end.

The RDY (L) terminal is disposed next to the GND (L) terminal, i.e., ata sixth position from the leading end, the DATAB (L) terminal isdisposed next to the RDY (L) terminal, i.e., at a seventh position fromthe leading end, the CLK (L) terminal is disposed next to the DATAB (L)terminal, i.e., at an eighth position from the leading end, the DATAL(L) terminal is disposed next to the CLK (L) terminal, i.e., at a ninthposition from the leading end, the HCLK (L) terminal is disposed next tothe DATAL (L) terminal, i.e., at a 10th position from the leading endand the HDATA (L) terminal is disposed next to the HCLK (L) terminal,i.e., at the trailing end.

Next, ramifications of noise attributable to communication linesconfigured with the individual body-side terminals and lens-sideterminals will be described. Hotline communication, through whichinformation is unidirectionally transmitted to the camera body 2 oncethe communication commences, is executed with a high frequency (executedrepeatedly over a fairly short cycle). During hotline communication, aclock signal (H clock signal) originating on the interchangeablelens-side is transmitted from the HCLK (L) terminal to the HCLK (B)terminal. A clock signal, which repeatedly shifts between high level andlow level over a short cycle, may become a source of significant noisewith respect to another signal. Furthermore, since the clock signal (Hclock signal) originating on the interchangeable lens-side, which istransmitted from the HCLK (L) terminal to the HCLK (B) terminal, isoutput from the interchangeable lens 3, noise which is carriederroneously in the clock signal cannot be detected by the camera body 2.This means that there is a possibility of the clock signal (H clocksignal) flowing through the HCLK terminals becoming a noise source andthat there is also a possibility of noise being included in the clocksignal (H clock signal), which, in turn, may cause an erroneousoperation of the camera 1. Examples of such an erroneous operationinclude the interchangeable lens erroneously detected as mounted and anincorrect decision made with respect to whether or not command datacommunication is enabled.

In the embodiment, the HCLK terminal is disposed at a position set apartfrom the VBAT terminal, which carries a high voltage. Thevoltage/current provided through the VBAT terminal to drive the lensdrive unit 33 in the interchangeable lens 3 fluctuates in correspondenceto the drive condition at the lens drive unit 33 and fluctuations in thevoltage/current at the VBAT terminal may result in noise at otherterminals. Accordingly, the VBAT terminal is disposed at a distance awayfrom the HCLK terminal so as to minimize the extent to which noiseattributable to fluctuations in the voltage/current at the VBAT terminalaffects the clock signal (H clock signal). Namely, noise is not allowedto enter the clock signal (H clock signal).

As explained earlier, the RDY terminal is used to indicate whether ornot command communication is enabled. In the embodiment, the HCLKterminal, which may become a noise source, is disposed at a distanceaway from the RDY terminal. As a result, it is ensured that noiseattributable to the clock signal (H clock signal) does not affect thesignal transmitted through the RDY terminal.

In addition, the HDATA terminal and the DATAL terminal are disposed nextto the HCLK terminal on the two sides thereof. This positionalarrangement makes it possible to minimize any adverse effect of noisefrom the HCLK terminal on terminals other than the HDATA terminal andthe DATAL terminal. Signals transmitted via the HDATA terminal and theDATAL terminal do not fluctuate as much as the clock signal (H clocksignal). Thus, any adverse effect attributable to fluctuation of theclock signal (H clock signal) on terminals other than the HDATA terminaland the DATAL terminal can be suppressed.

Through command data communication, information is bidirectionallytransmitted/received between the camera body 2 and the interchangeablelens 3, as explained earlier. For command data communication, a clocksignal (C clock signal) originating on the camera body-side istransmitted from the CLK (B) terminal to the CLK (L) terminal. The clocksignal (C clock signal) transmitted through the CLK terminal, too, maybecome a noise source for the same reason as that explained above.

In addition, if noise enters the clock signal (C clock signal), an errorwill occur in the command data communication. Accordingly, the CLKterminal is disposed at a position away from the VBAT terminal, to whicha high voltage is applied in the embodiment. The voltage/currentprovided via the VBAT terminal to drive the lens drive unit 33 in theinterchangeable lens 3 fluctuates in correspondence to the drivecondition at the lens drive unit 33 and fluctuations in thevoltage/current at the VBAT terminal may result in noise at otherterminals. Accordingly, the VBAT terminal is disposed at a distance awayfrom the CLK terminal so as to minimize the extent to which noiseattributable to fluctuations in the voltage/current at the VBAT terminalaffects the clock signal (C clock signal). Namely, it is arranged thatnoise is not allowed to enter the clock signal (C clock signal).

Furthermore, the CLK terminal is disposed at a position set apart fromthe RDY terminal used to indicate whether or not command communicationis enabled, so as not to be adjacent to the RDY terminal.

Moreover, if the HCLK terminal and the CLK terminal are disposedadjacent to each other, one clock signal may affect the other clocksignal, resulting in an occurrence of noise. In the embodiment, theDATAL terminal is disposed between the CLK terminal and the HCLKterminal. In addition, the DATAB terminal is disposed between the CLKterminal and the RDY terminal. Namely, the DATAL terminal and the DATABterminal are disposed next to the CLK terminal on the two sides thereof.This positional arrangement makes it possible to minimize the extent towhich noise originating at the CLK terminal affects the camera 1.Signals transmitted via the DATAL terminal and the DATAB terminal do notfluctuate as much as the clock signal (C clock signal), and thus, anyadverse effect attributable to fluctuation of the clock signal (C clocksignal) on terminals other than the DATAL terminal and the DATABterminal can be suppressed.

By disposing the DATAL terminal between the CLK terminal and the HCLKterminal, the extent to which the clock signal (H clock signal) at theHCLK terminal is adversely affected by fluctuations in the clock signal(C clock signal) at the CLK terminal and the extent to which the clocksignal (C clock signal) at the CLK terminal is adversely affected byfluctuations in the clock signal (H clock signal) at the HCLK terminalcan be minimized, since the signal passing through the DATAL terminaldoes not fluctuate as much as the clock signal (C clock signal) at theCLK terminal or the clock signal (H clock signal) at the HCLK terminal.

As explained earlier, the signal level at the RDY terminal needs to bedetermined in order to carry out command data communication. This meansthat since the signal level at the RDY terminal indicates whether or notcommand data communication can be carried out, noise in the signal isbound to significantly affect photographing operations. For instance, asituation may arise in which noise causes the body control unit 27 toerroneously ascertain that communication is enabled even when commanddata communication cannot be carried out. In this situation, even thoughthe lens control unit 37 cannot actually receive command data, the bodycontrol unit 27 will transmit command data and erroneously assume thatcontrol instructions in the command data are executed in theinterchangeable lens 3. However, the control instructions in the commanddata having been erroneously transmitted will not be executed, since thelens control unit 37 cannot receive the command data. As a result, aproblem will occur in the operation of the camera 1. For this reason, itis necessary to ensure that noise does not enter the signal transmittedthrough the RDY terminal. It is preferable that terminals carryingrelatively stable signals, i.e., signals with small shifts in the signallevel per unit time, be disposed next to an RDY terminal on the twosides thereof, in order to ensure that noise does not enter the signalat the RDY terminal. In the embodiment, the GND terminal and the DATABterminal are disposed next to the RDY terminal on the two sides thereof.The GND terminal is a stable terminal assuming the ground potential, andthe DATAB terminal is also a stable terminal through which a stablesignal, in comparison to the signals passing through the CLK terminaland the HCLK terminal is transmitted. By adopting this positionalarrangement, the extent to which the signal at the RDY terminal isaffected by noise can be minimized.

Electric power (source voltage) provided from the VBAT (B) terminal tothe VBAT (L) terminal is used to drive the actuator (e.g., a steppingmotor) in the lens drive unit 33 at the interchangeable lens 3. Thismeans that the electric current flowing through the VBAT terminalsfluctuates greatly as the actuator shifts from a drive state to anon-drive state or vice versa. Such fluctuations in the electric currentmay become a cause of noise in signals passing through other terminals.In the embodiment, the VBAT terminals are each disposed at a positionset apart from the corresponding RDY terminal, DATAB terminal, CLKterminal and DATAL terminal used for command data communication and alsoset apart from the corresponding HCLK terminal and HDATA terminal usedfor hotline communication. In addition, the GND terminal, the V33terminal and the PGND terminal are disposed between the VBAT terminaland the terminals used for purposes of communication listed above. As aresult, the extent to which noise attributable to fluctuations in theelectric current flowing through the VBAT terminal affects datacommunication can be minimized.

The positional arrangement of the terminals to minimize the adverseeffects of noise, as described above, is summarized below.

The RDY terminal is disposed away from both the VBAT terminal and theHCLK terminal at which noise is likely to occur, i.e., at a positionthat is adjacent to neither the VBAT terminal nor the HCLK terminal.Through these measures, the adverse effect of noise on the RDY terminalused to indicate whether or not command data communication is enabledcan be minimized.

The HCLK terminal at which noise is likely to occur is disposed betweenthe HDATA terminal and the DATAL terminal, whereas the CLK terminal isdisposed between the DATAL terminal and the DATAB terminal. Namely, theHDATA terminal, the HCLK terminal, the DATAL terminal, the CLK terminaland the DATAB terminal are disposed in this order, starting from thetrailing end along the mounting direction. As a result, the extent towhich noise attributable to a clock signal adversely affects the RDYterminal or the like can be minimized.

Moreover, the terminal group used for power supply and the terminalgroup engaged in communication are disposed away from each other on thetwo sides of the RDY terminal so as to minimize the adverse effect ofnoise. In more specific terms, on the leading-end side along themounting direction relative to the RDY terminal, the VBAT terminal, thePGND terminal, the V33 terminal and the GND terminal, used for purposesof power supply, are disposed in this order starting from the leadingend, and on the trailing-end side along the mounting direction relativeto the RDY terminal, the DATAB terminal, the CLK terminal, the DATALterminal, the HCLK terminal and the HDATA terminal used forcommunication are disposed in this order starting from the leading-endside. Through these measures, the extent to which the communicationterminals are affected by the power supply system terminal group, whichincludes the VBAT terminal, can be minimized. In addition, the extent towhich noise from the power supply system terminal group, which includesthe VBAT terminal, and noise from the communication terminal group,which includes the HCLK terminal and the CLK terminal, affects the RDYterminal can be minimized.

The HCLK terminal, through which a clock signal originating on theinterchangeable lens-side is transmitted in hotline communication, isdisposed at a position further away from the corresponding VBAT terminalthan the CLK terminal through which a clock signal originating on thecamera body side is transmitted for command data communication. Therationale for this positional arrangement is that while the clock signaltransmitted to the interchangeable lens 3 through the CLK terminals isoutput by the body control unit 27 via the first body communication unit28, noise in the clock signal output from the interchangeable lens 3 viathe second lens communication unit 39 and transmitted through the HCLK(L) terminal to the camera body 2 will affect the camera 1 to a greaterextent since noise in the clock signal transmitted from theinterchangeable lens will cause the body control unit 27 to make anerroneous decision.

The HCLK terminal is disposed at a position set apart from the VBATterminal by a greater distance than the GND terminal. In addition, thePGND terminal is disposed between the GND terminal and the VBATterminal. This positional arrangement makes it possible to shield theHCLK terminal, through which a clock signal used in hotlinecommunication is transmitted, from noise originating at the VBATterminal.

The CLK terminal is disposed at a position set apart from the VBATterminal by a greater distance than the GND terminal. In addition, thePGND terminal is disposed between the GND terminal and the VBATterminal. This positional arrangement makes it possible to shield theCLK terminal, through which a clock signal used in command datacommunication is transmitted, from noise originating at the VBATterminal.

The interchangeable lens 3 and the camera body 2 are engaged in commanddata communication through which an RDY signal, a CLK signal, a DATABsignal and a DATAL signal are exchanged via the first lens communicationunit 38 and the first body communication unit 28 as described above byusing the terminal groups assuming the positional arrangement describedabove. In addition, the interchangeable lens 3 and the camera body 2 areengaged in hotline communication through which an HCLK signal and anHDATA signal are transmitted via the second lens communication unit 39and the second body communication unit 29. It is to be noted thatcommand data communication is carried out through a communication pathseparate from the communication path through which hotline communicationis carried out and thus, command data communication and hotlinecommunication can be executed concurrently. Namely, even while the firstlens communication unit 38 is engaged in command data communication withthe first body communication unit 28, the second lens communication unit39 is able to carry out hotline communication with the second bodycommunication unit 29 as needed. Furthermore, even while the second lenscommunication unit 39 is engaged in hotline communication with thesecond body communication unit 29, the first lens communication unit 38is able to carry out command data communication with the first bodycommunication unit 28 as needed.

Positional Arrangement of Terminals Taking into Consideration TerminalWear

The following is a description of how the various terminals come intocontact with one another when the interchangeable lens is mounted at ordismounted from the camera body 2.

When the interchangeable lens 3 is being mounted at the camera body 2, abody-side terminal comes into contact with lens-side terminals one afteranother. Likewise, it comes into contact with lens-side terminals whenthe interchangeable lens 3 is being dismounted from the camera body 2.In other words, the body-side terminals constituted with pins projectingout from the body-side connection unit 202 each slide against lens-sideterminals constituted with exposed conductive contact surfaces one afteranother. Since a plurality of interchangeable lenses can be mounted at asingle camera body, the body-side terminals tend to become worn morereadily than the lens-side terminals. In particular, a body-sideterminal disposed at a position closer to the trailing end along themounting direction of the interchangeable lens 3, which slides against agreater number of lens-side terminals, is bound to be subjected togreater friction and become worn to a greater extent. This means that abody-side terminal located closer to the trailing end tends to becomemore worn at the tip of the pin compared to a body-side terminaldisposed at a position closer to the leading end. Wear at a body-sideterminal affects contact with the corresponding lens-side terminal,which may, in turn, lead to unstable data communication.

In the embodiment, the LDET (B) terminal is disposed at the leading endposition along the mounting direction and thus, the LDET (B) terminal isbound to be the least worn terminal. As a result, since good contactbetween the LDET (B) terminal and the LDET (L) terminal is assured,there is less likelihood of erroneously sensing the interchangeable lens3 to be in a mounted or dismounted state.

As explained earlier, the CLK (B) terminal and the HCLK (B) terminal aredisposed at positions set apart from the VBAT terminal so as to minimizethe adverse effect of noise on communication. Namely, the CLK (B)terminal and the HCLK (B) terminal are disposed on the trailing-end sideaway from the VBAT terminal disposed at the second position from theleading-end along the mounting direction. This means that the CLK (B)terminal and HCLK (B) terminal are likely to be worn to a greater extentcompared to the LDET (B) terminal and the VBAT (B) terminal. In theembodiment, the CLK (B) terminal and the HCLK (B) terminal are disposednear or just beside the body-side first claw portion 129 a. Namely, theCLK (B) terminal and the HCLK (B) terminal are disposed at positionscloser to the inner circumferential edge located on the innercircumferential side of the body-side first claw portion 129 a, comparedto the VBAT (B) terminal. In more specific terms, the distance betweenthe CLK (B) terminal and the inner circumferential edge of the body-sidefirst claw portion 129 a is smaller than the distance between the VBAT(B) terminal and the inner circumferential edge of the body-side firstclaw portion 129 a, and the distance between the HCLK (B) terminal andthe inner circumferential edge of the body-side first claw portion 129 ais smaller than the distance between the VBAT (B) terminal and the innercircumferential edge of the body-side first claw portion 129 a. Asexplained earlier, the first plate spring 141 a is disposed on the backside of the body-side first claw portion 129 a and the lens-side firstclaw portion 139 a is pressed toward the +Z direction (see FIG. 1) viathe first plate spring 141 a.

In relation to the first plate spring 141 a, too, the distance betweenthe CLK (B) terminal and the first plate spring 141 a and the distancebetween the HCLK (B) terminal and the first plate spring 141 a are bothsmaller than the distance between the VBAT (B) terminal and the firstplate spring 141 a. This positional relationship with regard to the VBAT(B) terminal is also applicable with respect to the LDET (B) terminal,i.e., the distance between the CLK (B) terminal and the first platespring 141 a and the distance between the HCLK (B) terminal and thefirst plate spring 141 a are both smaller than the distance between theLDET (B) terminal and the first plate spring 141 a. The CLK (B) terminaland the HCLK (B) terminal disposed by adopting this positionalarrangement are pressed against the corresponding lens-side terminalswith more force compared to the VBAT (B) terminal and the LDET (B)terminal.

On the lens-side, too, the CLK (L) terminal and the HCLK (L) terminalare disposed at positions closer to the inner circumferential edge ofthe lens-side first claw portion 139 a compared to the VBAT (L)terminal. Namely, the distance between the CLK (L) terminal and theinner circumferential edge of the lens-side first claw portion 139 a issmaller than the distance between the VBAT (L) terminal and the innercircumferential edge of the lens-side first claw portion 139 a and thedistance between the HCLK (L) terminal and the inner circumferentialedge of the lens-side first claw portion 139 a is smaller than thedistance between the VBAT (L) terminal and the inner circumferentialedge of the lens-side first claw portion 139 a. This means that in amount-complete state, the CLK (L) terminal and the HCLK (L) terminallocated near the lens-side first claw portion 139 a are pressed againstthe corresponding body-side terminals via the first plate spring 141 a.

The positional relationship with respect to the VBAT (L) also applieswith respect to the LDET (L) terminal and thus, the distance between theCLK (L) terminal and the first plate spring 141 a and the distancebetween the HCLK (L) terminal and the first plate spring 141 a are bothsmaller than the distance between the LDET (L) terminal and the firstplate spring 141 a in a mount-complete state. As a result, greater forceis applied in a mount-complete state to press the CLK (L) terminal andthe HCLK (L) terminal toward the corresponding body-side terminalscompared to the force applied to the LDET (L) terminal. Thus, goodcontact can be sustained even when the CLK (B) terminal or the HCLK (B)terminal becomes worn, which, in turn, makes it possible to stabilizethe respective clock signals to assure stable data communication.Furthermore, even if the camera body 2 or the interchangeable lens 3 issubjected to a shock while sustaining a mount-complete state, thecontact between the CLK (B) terminal and the CLK (L) terminal and thecontact between the HCLK (B) terminal and the HCLK (L) terminal aremaintained.

Even when the lens-side first claw portion 139 a includes a notchportion, the total area made up with the projecting portion and thenotch portion disposed so as to face opposite the body-side first clawportion 129 a constitutes a lens-side first claw portion. Such a notchportion may be formed by dividing the lens-side claw portion into two ormore segments separated along the circumferential direction, by notchingpart of the lens-side claw portion, or by notching at least part of thelens-side claw portion so as to reduce the length of the part measuredalong the radial direction. In addition, the length of the lens-sideclaw portion, measured along the circumferential direction, may beadjusted as long as it is allowed to pass through the correspondingbody-side through portion. The same principle applies to the lens-sidesecond claw portion 139 b, the lens-side third claw portion 139 c andthe lens-side fourth claw portion 139 d. Moreover, the thickness of thecylindrical portion, measured along the radial direction, may beadjusted as needed, and the cylindrical portion may adopt a shape withat least part thereof projecting further inward relative to thecylindrical portion in the embodiment.

As explained above, the CLK (B) terminal and the HCLK (B) terminal arebound to become worn to a greater extent compared the LDET (B) terminaland the VBAT (B) terminal. In the embodiment, the CLK (B) terminal andthe HCLK (B) terminal are disposed near the body-side first claw portion129 a. Namely, the CLK (B) terminal and the HCLK (B) terminal aredisposed at positions closer to the inner circumferential edge of thebody-side first claw portion 129 a than the LDET (B) terminal and theVBAT (B) terminal. This means that the distance between the CLK (B)terminal and the inner circumferential edge of the body-side first clawportion 129 a is smaller than the distance between the LDET (B) terminalor the VBAT (B) terminal and the inner circumferential edge of thebody-side first claw portion 129 a, and also, the distance between theHCLK (B) terminal and the inner circumferential edge of the body-sidefirst claw portion 129 a is smaller than the distance between the LDET(B) terminal or the VBAT (B) terminal and the inner circumferential edgeof the body-side first claw portion 129 a. As explained earlier, thefirst plate spring 141 a is present on the back side of the body-sidefirst claw portion 129 a and the lens-side first claw portion 139 a ispressed toward the +Z direction (see FIG. 1) by the first plate spring141 a. In relation to the first plate spring 141 a, too, the distancebetween the CLK (B) terminal and the first plate spring 141 a and thedistance between the HCLK (B) terminal and the first plate spring 141 aare both smaller than the distance between the LDET (B) terminal or theVBAT (B) terminal and the first plate spring 141 a.

On the lens-side, too, the CLK (L) terminal and the HCLK (L) terminalare disposed at positions closer to the inner circumferential edge ofthe lens-side first claw portion 139 a compared to the LDET (L) terminaland the VBAT (L) terminal. In other words, the distance between the CLK(L) terminal and the inner circumferential edge of the lens-side firstclaw portion 139 a is smaller than the distance between the LDET (L)terminal or the VBAT (L) terminal and the inner circumferential edge ofthe lens-side first claw portion 139 a, and the distance between theHCLK (L) terminal and the inner circumferential edge of the lens-sidefirst claw portion 139 a is smaller than the distance between the LDET(L) terminal or the VBAT (L) terminal and the inner circumferential edgeof the lens-side first claw portion 139 a. As a result, the CLK (L)terminal and the HCLK (L) terminal located near the lens-side first clawportion 139 a are pressed against the corresponding body-side terminalsby the first plate spring 141 a. Thus, greater force is applied to pressthe CLK (B) terminal and the HCLK (B) terminal toward the correspondinglens-side terminals compared to the force applied to the LDET (B)terminal and the VBAT (B) terminal. Consequently, good contact can besustained even when the CLK (B) terminal or the HCLK (B) terminalbecomes worn, to assure stable data communication. Furthermore, even ifthe camera body 2 or the interchangeable lens 3 is subjected to a shockwhile sustaining a mount-complete state, the contact between the CLK (B)terminal and the corresponding lens-side terminal and the contactbetween the HCLK (B) terminal and the corresponding lens-side terminalare maintained.

In the embodiment, the CLK (B) terminal and the HCLK (B) terminal aredisposed also close to the body-side fourth claw portion 129 d. In otherwords, the CLK (B) terminal and the HCLK (B) terminal are disposed atpositions closer to the body-side fourth claw portion 129 d compared tothe VBAT (B) terminal and the LDET (B) terminal. This means that thedistance between the CLK (B) terminal and the body-side fourth clawportion 129 d is smaller than the distance between the VBAT (B) terminalor the LDET (B) terminal and the body-side fourth claw portion 129 d,and the distance between the HCLK (B) terminal and the body-side fourthclaw portion 129 d is smaller than the distance between the VBAT (B)terminal or the LDET (B) terminal and the body-side fourth claw portion129 d. As explained earlier, the fourth plate spring 141 d is present onthe back side of the body-side fourth claw portion 129 d, and thelens-side fourth claw portion 139 d is pressed toward the +Z direction(see FIG. 1) by the fourth plate spring 141 d. As a result, the CLK (B)terminal and the HCLK (B) terminal located close to the lens-side fourthclaw portion 139 d are pressed against the corresponding lens-sideterminals with greater force and in a more stable manner via the firstplate spring 141 a and the fourth plate spring 141 d, compared to theVBAT (B) terminal and the LDET (B) terminal.

The distance between the CLK (B) terminal and the body-side first clawportion 129 a (a similar principle applies with respect to the distancebetween the CLK (B) terminal and the body-side fourth claw portion 129d, although an explanation is not provided) mentioned above refers tothe distance in a straight line between one end of the body-side firstclaw portion 129 a and the CLK (B) terminal, but the distance may bealternatively defined as the distance in a straight line between theother end of the body-side first claw portion 129 a and the CLK (B)terminal. As a further alternative, the distance between the CLK (B)terminal and the body-side first claw portion 129 a may be defined asthe straight line distance between the halfway position in the body-sidefirst claw portion 129 a along the circumference of the body-side mountunit 201 and the CLK (B) terminal. The distance between anotherbody-side terminal, such as the HCLK (B) terminal, the VBAT (B) terminalor the LDET (B) terminal and the body-side first claw portion 129 a islikewise a straight line distance between the terminal and the body-sidefirst claw portion 129 a. In addition, the distance between the firstplate spring 141 a (the fourth plate spring 141 d, as well) and abody-side terminal is likewise a straight line distance.

It is to be noted that the distance between the CLK (B) terminal and thebody-side first claw portion 129 a (a similar principle applies withrespect to the distance between the CLK (B) terminal and the body-sidefourth claw portion 129 d, although an explanation is not provided)mentioned above may refer to the distance measured along the circulararc connecting one end of the body-side first claw portion 129 a and theCLK (B) terminal along the circumference of the body-side mount unit201, or it may be alternatively defined as the distance measured alongthe circular arc connecting the other end of the body-side first clawportion 129 a and the CLK (B) terminal. As a further alternative, thedistance between the CLK (B) terminal and the body-side first clawportion 129 a may be defined as the distance measured along the circulararc connecting the halfway position in the body-side first claw portion129 a along the circumference of the body-side mount unit 201 and theCLK (B) terminal. The distance between another body-side terminal, suchas the HCLK (B) terminal, the VBAT (B) terminal or the LDET (B) terminaland the body-side first claw portion 129 a may also be defined as thedistance measured along the circular arc connecting the terminal and thebody-side first claw portion 129 a. In addition, the distance betweenthe first plate spring 141 a (the fourth plate spring 141 d, as well)and a body-side terminal may likewise be defined as the distancemeasured along the circular arc.

While a description above relates to the camera body 2, a similardescription applies to the interchangeable lens 3. In the embodiment,the CLK (L) terminal and the HCLK (L) terminal are disposed near thelens-side first claw portion 139 a. In other words, the CLK (L) terminaland the HCLK (L) terminal are disposed at positions closer to thelens-side first claw portion 139 a compared to the VBAT (L) terminal andthe LDET (L) terminal. This means that the distance between the CLK (L)terminal and the lens-side first claw portion 139 a is smaller than thedistance between the VBAT (L) terminal or the LDET (L) terminal and thelens-side first claw portion 139 a, and the distance between the HCLK(L) terminal and the lens-side first claw portion 139 a is smaller thanthe distance between the VBAT (L) terminal or the LDET (L) terminal andthe lens-side first claw portion 139 a. The lens-side first claw portion139 a is pressed toward the +Z direction (see FIG. 1) by the first platespring 141 a located on the body-side. Thus, the CLK (L) terminal andthe HCLK (L) terminal located near the lens-side first claw portion 139a are pressed toward the corresponding body-side terminals with greaterforce imparted by the first plate spring 141 a, compared to the VBAT (L)terminal and the LDET (L) terminal, in much the same way as thatdescribed earlier.

In the embodiment, the CLK (B) terminal and the HCLK (B) terminal aredisposed within a fan-shaped area (ranging over an angle 50) defined bythe central position of the opening at the body-side mount unit 201(i.e., the position of the optical axis L of the interchangeable lens 3)and the body-side first claw portion 129 a assuming a circular arc shapeas shown in FIG. 4A. In other words, the CLK (B) terminal and the HCLK(B) terminal are disposed inside a triangular area defined by thecentral position of the opening at the body-side mount unit 201 (i.e.,the position of the optical axis L of the interchangeable lens 3) andthe two ends of the body-side first claw portion 129 a located on theinner circumferential side. That is, while the body-side first clawportion 129 a is not present on a line extending from a one-point chainline 151 connecting the central position of the opening at the body-sidemount unit 201 and the LDET (B) terminal, the body-side first clawportion 129 a is present on a line extending from a one-point chain line152 connecting the central position of the opening at the body-sidemount unit 201 and the HCLK (B) terminal and the body-side first clawportion 129 a is present on a line extending from a one-point chain line153 connecting the central position of the opening at the body-sidemount unit 201 and the CLK (B) terminal. As a result, the CLK (B)terminal and the HCLK(B) terminal are pressed against the correspondinglens-side terminals with greater force in a mount-complete statecompared to the LDET (B) terminal.

The CLK (L) terminal and the HCLK (L) terminal are disposed within afan-shaped area (ranging over an angle 60) defined by the centralposition of the opening at the lens-side mount unit 301 (i.e., theposition of the optical axis L of the interchangeable lens 3) and thelens-side first claw portion 139 a assuming a circular arc shape, asshown in FIG. 5. In other words, the CLK (L) terminal and the HCLK (L)terminal are disposed inside a triangular area defined by the centralposition of the opening at the lens-side mount unit 301 (i.e., theposition of the optical axis L of the interchangeable lens 3) and thetwo ends of the lens-side first claw portion 139 a located on the outercircumferential side. That is, while the lens-side first claw portion139 a is not present on a line extending from a one-point chain line 161connecting the central position of the opening at the lens-side mountunit 301 and the LDET (L) terminal, the lens-side first claw portion 139a is present on a line extending from a one-point chain line 162connecting the central position of the opening at the lens-side mountunit 301 and the HCLK (L) terminal and the lens-side first claw portion139 a is present on a line extending from a one-point chain line 163connecting the central position of the opening at the lens-side mountunit 301 and the CLK (L) terminal. As a result, the CLK (L) terminal andthe HCLK (L) terminal contact the corresponding body-side terminals in amore stable manner compared to the LDET (L) terminal in a mount-completestate. Namely, greater force is applied to the CLK (L) terminal and theHCLK (L) terminal to press them toward the corresponding body-sideterminals than to the LDET (L) terminal. Thus, even when the tips of theCLK (B) terminal and the HCLK (B) terminal have become worn, clocksignals can be exchanged between the camera body 2 and theinterchangeable lens 3 in a stable manner.

It is to be noted that while the explanation has been given on the CLK(B) terminal, the CLK (L) terminal, the HCLK (B) terminal and the HCLK(L) terminal, the similar concept may apply to the other communicationsystem terminals, i.e., the HDATA (B) terminal, the HDATA (L) terminal,the DATAL (B) terminal, the DATAL (L) terminal, the DATAB (B) terminaland the DATAB (L) terminal. Namely, the HDATA (B) terminal, the DATAL(B) terminal and the DATAB (B) terminal are disposed at positions closer(at shorter distances) to the body-side first claw portion 129 a and thefirst plate spring 141 a, compared to the LDET (B) terminal and the VBAT(B) terminal. As a result, the HDATA (B) terminal, the DATAL (B)terminal and the DATAB (B) terminal are pressed toward the correspondinglens-side terminals with greater force compared to the VBAT (B) terminaland the LDET (B) terminal, so as to maintain good contact with thelens-side terminals. In addition, the HDATA (L) terminal, the DATAL (L)terminal and the DATAB (L) terminal are disposed at positions closer (atshorter distances) to the lens-side first claw portion 139 a and thefirst plate spring 141 a compared to the LDET (L) terminal and the VBAT(L) terminal. As a result, the HDATA (L) terminal, the DATAL (L)terminal and the DATAB (L) terminal are pressed toward the correspondingbody-side terminals with greater force compared to the VBAT (L) terminaland the LDET (L) terminal, so as to maintain good contact with thebody-side terminals.

Through command data communication, values representing communicationspecifications or communication conditions for hotline communication aretransmitted and received between the interchangeable lens 3 and thecamera body 2. Such a value will be referred to as a generation. A valuerepresenting a generation may be otherwise referred to as generationinformation. While a generation is normally represented by an integerequal to or greater than 0, it may instead be represented by a decimalnumber. Furthermore, a generation may be referred to as a grade. FIG. 6is a chart presenting examples of generations. Different generationsrepresent sets of communication specifications different from oneanother. The communication specifications may be otherwise referred toas a communication system, a communication method or a communicationstandard. The communication specifications include at least one itemrelated to communication, that is, at least one condition under whichcommunication is carried out. The sets of communication specificationsin the examples presented in FIG. 6 each include threecommunication-related items, i.e., a hotline communication speed, ahotline communication interval and a quantity of sets of datatransmitted through hotline communication. The communicationspecifications designated as a generation do not need to include thesethree items and may instead include one or two items selected from thesethree items.

Such generations may be, for instance, first through fourth generationsdifferent from one another. The sets of communication specificationsdesignated as the various generations are different from one another.However, the sets of communication specifications designated asdifferent generations may include an item indicating matching values. Itis to be noted that a generation bearing a higher number is referred toas a higher-order generation (grade). For instance, the fourthgeneration is a higher-order generation (grade) relative to the thirdgeneration. Furthermore, a generation may represent another set ofspecifications in addition to the communication specifications. In theexamples presented in FIG. 6, each generation represents specificationsrelated to a sampling interval for data generation, in addition to thecommunication specifications. Moreover, generations may furtherrepresent, for instance, specifications related to vibration correctionfunction/capability in addition to the specifications described above.

The communication speed is the rate at which data are communicatedthrough hotline communication (i.e., clock frequency). In other words,the communication speed is the speed at which data are transferred fromthe second lens communication unit 39 to the second body communicationunit 29. The communication interval is the time interval at which dataare transferred through hotline communication. The data transmitted fromthe interchangeable lens 3 to the camera body 2 through hotlinecommunication may be information pertaining to focus lens drive(information related to the position of the focus lens and the like),information pertaining to anti-vibration lens drive (information relatedto the position of the anti-vibration lens and the like), informationpertaining to the zoom lens (information pertaining to the state of thezoom lens, focal length information and the like), and informationpertaining to drive of the aperture stop 32 (information related to theF-number). In addition, the sampling interval is a time interval overwhich data to be transmitted through hotline communication are sampled.Such a time interval may be, for instance, the interval over which thelens control unit 37 samples pulse signals generated by the lensposition detection unit 34.

The communication specifications designated as the first generation inFIG. 6 indicate V1 (in units of, for instance, MHz) for thecommunication speed, T1 (indicated in units of, for instance, msec) forthe communication interval and N1 (integer) for the number of sets ofdata. A generation bearing a higher number (higher grade) indicates ahigher communication speed, a shorter communication interval and agreater number of sets of data. Namely, the communication specificationsdesignated as the second generation indicate V2 higher than V1 for thecommunication speed, T2 shorter than T1 for the communication intervaland N2 greater than N1 for the number of sets of data.

The communication specifications designated as the third generationindicates V3 higher than V2 for the communication speed, T3 shorter thanT2 for the communication interval and N3 greater than N2 for the numberof sets of data. The communication specifications designated as thefourth generation indicate V4 higher than V3 for the communicationspeed, T4 shorter than T3 for the communication interval and N4 greaterthan N3 for the number of sets of data. It is to be noted that V1through V4, T1 through T4 and N1 through N4 may each be a specific fixedvalue or they may be values falling into a specific range. For instance,the communication speed V1 may be a predefined fixed value (e.g., 2.5MHz) or it may be a predefined communication speed range v1 through v2(e.g., 2 through 8 MHz). In addition, the communication interval T1 maybe a predefined fixed value (e.g., 1 msec) or it may be a predefinedcommunication interval range (0.5 through 2 msec).

The data transmitted through hotline communication may be informationpertaining to focus lens drive, anti-vibration lens drive, aperture stopdrive or the state of the zoom lens, as explained earlier. When thenumber of sets of data is N1, for instance, the data transmitted throughhotline communication is information pertaining to focus lens drive.When the number of sets of data is N2, information pertaining toanti-vibration lens drive is also transmitted through hotlinecommunication, in addition to information pertaining to focus lensdrive. When the number of sets of data is N3, information pertaining tothe drive of the aperture stop 32, as well as information related focuslens drive and information pertaining to anti-vibration lens drive, istransmitted through hotline communication. When the number of sets ofdata is N4, information pertaining to the zoom lens state is transmittedthrough hotline communication, in addition to information pertaining tofocus lens drive, information pertaining to anti-vibration lens driveand information pertaining to drive of the aperture stop 32.

In the examples presented in FIG. 6 described above, the number of setsof data transmitted through hotline communication is included in thecommunication specifications designated as a given generation. However,the number of sets of data does not need to be included in thecommunication specifications and instead may be separately representedby the corresponding generation. In addition, the generations eachrepresent a specific number of sets of data in the examples describedearlier. As an alternative, each generation may indicate the data thatare transmitted through hotline communication. Namely, a generation mayindicate the data to be transmitted through hotline communication, suchas information pertaining to focus lens drive (information related tothe position of the focus lens and the like), information pertaining toanti-vibration lens drive (information related to the position of theanti-vibration lens and the like), information pertaining to the zoomlens (information related to the zoom lens state, focal lengthinformation and the like), and information pertaining to drive of theaperture stop 32 (information pertaining to the F-number and the like).

In addition, the sampling interval specifications designated as thefirst generation indicate S1 (in units of, for instance msec) in theexample in FIG. 6. The sampling interval specifications designated asthe second generation indicate S2, shorter than S1, the samplinginterval specifications designated as the third generation indicate S3,shorter than S2, and the sampling interval specifications designated asthe fourth generation indicate S4, shorter than S3. S1 through S4 mayeach be a predefined fixed value or may each be values falling into apredefined range.

It is to be noted that all of the items included in the communicationspecifications and other specifications do not need to indicatedifferent values from one generation (grade) to another generation(grade) among the first through fourth generations, and instead, asingle item or a plurality of items corresponding to a given generationmay indicate values different from those in another generation. Forinstance, while the communication speed increases in a highergeneration, the communication interval and the number of sets of datamay remain unchanged in the higher generation. In addition, the varioushotline communication generations may each represent sampling intervalspecifications and specifications related to vibration correctionfunction/capability, in addition to the communication specifications. Insuch a case, only one item included in the communication specificationsmay indicate different values from one generation to another, two orthree items included in the communication specifications may indicatedifferent values from one generation to another, or the samplinginterval specifications and the specifications related to the vibrationcorrection function/capability in addition to the communicationspecifications, may all indicate different values from one generation toanother.

Next, the relationship among the communication specifications designatedas specific generations, the interchangeable lens 3 and the camera body2 will be explained. An interchangeable lens 3 and a camera body 2 thatare able to carry out hotline communication according to thecommunication specifications designated as the first generation will berespectively referred to as a first-generation interchangeable lens 3and a first-generation camera body 2. In addition, an interchangeablelens 3 and a camera body 2 that are able to carry out hotlinecommunication according to the communication specifications designatedas the second generation will be respectively referred to as asecond-generation interchangeable lens 3 and a second-generation camerabody 2. Likewise, an interchangeable lens 3 and a camera body 2 that areable to carry out hotline communication in conformance to thecommunication specifications designated as the third generation will berespectively referred to as a third-generation interchangeable lens 3and a third-generation camera body 2. An interchangeable lens 3 and acamera body 2 that are able to carry out hotline communication inconformance to the communication specifications designated as the fourthgeneration will be respectively referred to as a fourth-generationinterchangeable lens 3 and a fourth-generation camera body 2.

It is to be noted that in the present embodiment, a plurality ofinterchangeable lenses and a plurality of camera bodies having functionsthat enable them to carry out communication in conformance to the commoncommunication specifications categorized as the “communicationspecifications designated as the first generation” are collectivelyreferred to as, a “first-generation interchangeable lens” and a“first-generation camera body” respectively. This concept applies inrelation to interchangeable lenses and camera bodies supporting thecommunication specifications designated as the second generation, thethird generation and the fourth generation. The “communicationspecifications designated as the first generation” may be otherwisereferred to as “first communication specifications”. In addition, the“first-generation interchangeable lens” and the “first-generation camerabody” may be respectively referred to as a “first interchangeable lens”and a “first camera body”.

It is to be noted that an interchangeable lens 3 and a camera body 2corresponding to the communication specifications designated as a givengeneration are also able to carry out hotline communication inconformance to the communication specifications designated as apreceding generation (a generation bearing a lower number, i.e., a lowergrade). This means that while a first-generation interchangeable lens 3and a first-generation camera body 2 carry out hotline communication inconformance to the communication specification represented by the firstgeneration, a second-generation interchangeable lens 3 and asecond-generation camera body 2 are each able to support thecommunication specifications designated as the first generation as wellas the communication specifications designated as the second-generation.In addition, a third-generation interchangeable lens 3 and athird-generation camera body 2 are each able to support thecommunication specifications designated as the first through thirdgenerations and a fourth-generation interchangeable lens 3 and afourth-generation camera body 2 are each able to support thecommunication specifications designated as the first through fourthgenerations. If a fourth-generation interchangeable lens 3 and athird-generation camera body 2 are used in combination, hotlinecommunication can be carried out in conformance to any of thecommunication specifications they commonly support, i.e., thecommunication specifications designated as the third generation, thecommunication specifications designated as the second generation and thecommunication specifications designated as the first generation.However, since the camera body 2 does not support the communicationspecifications designated as the fourth generation, they cannot carryout hotline communication in conformance to the communicationspecifications designated as the fourth generation, or hotlinecommunication in conformance to the communication specificationsdesignated as the fourth generation will not be commenced.

FIG. 7 presents a chart indicating generations each representing thecommunication specifications in conformance to which hotlinecommunication is carried out by an interchangeable lens 3, correspondingto one of the first through fourth generations, and a camera body 2corresponding to one of the first through fourth generations, used incombination. FIG. 7 indicates the generations each representing thecommunication specification supported in hotline communication carriedout by a specific combination of a camera body 2 and an interchangeablelens 3, with generations pertaining to the camera body 2 indicated alongthe horizontal axis and generations pertaining to the interchangeablelens 3 indicated along the vertical axis.

As explained below, it is preferable to carry out hotline communicationin conformance to the communication specifications designated as thehighest-order generation (the generation bearing the highest number, themost advanced generation, or the highest grade) that can be assumed in agiven combination of an interchangeable lens 3 and a camera body 2.However, hotline communication may be carried out in conformance to thecommunication specifications designated as a lower-order generationinstead of the highest-order generation.

When a first-generation interchangeable lens 3 is mounted at a camerabody 2 corresponding to any generation among the first through fourthgenerations, hotline communication will be carried out in conformance tothe communication specifications designated as the first generation.

When a second-generation interchangeable lens 3 is mounted at a camerabody 2 corresponding to any of the first through fourth generations,hotline communication will be carried out in conformance to thecommunication specifications designated as the first generation providedthat the second-generation interchangeable lens 3 is mounted at afirst-generation camera body 2, and hotline communication will becarried out in conformance to the communication specificationsdesignated as the second generation provided that the second-generationinterchangeable lens 3 is mounted at a camera body 2 corresponding toany generation among the second through fourth generations.

Hotline communication will be carried out as described below when athird-generation interchangeable lens 3 is mounted at a camera body 2corresponding to a generation among the first through fourthgenerations. The third-generation interchangeable lens 3 will carry outhotline communication with a first-generation camera body 2 inconformance to the communication specifications designated as the firstgeneration, will carry out hotline communication with asecond-generation camera body 2 in conformance to the communicationspecifications designated as the second generation and will carry outhotline communication with a camera body 2 corresponding to the thirdgeneration or the fourth generation in conformance to the communicationspecifications designated as the third generation. It is to be notedthat the third-generation interchangeable lens 3 may engage incommunication with a second-generation camera body 2 in conformance tothe communication specifications designated as the first generation,i.e., a lower-order generation (a generation bearing a lower number, apreceding generation) instead of the communication specificationsdesignated as the highest-order generation (the generation bearing thehighest number, the most advanced generation, the highest grade), andmay engage in communication with a third-generation camera body 2 or afourth-generation camera body 2 in conformance to the communicationspecifications designated as the first generation or the secondgeneration.

Hotline communication will be carried out as described below when afourth-generation interchangeable lens 3 is mounted at a camera body 2corresponding to a generation among the first through fourthgenerations. The fourth-generation interchangeable lens 3 will carry outhotline communication with a first-generation camera body 2 inconformance to the communication specifications designated as the firstgeneration, and will carry out hotline communication with asecond-generation camera body 2 in conformance to the communicationspecifications designated as the second generation. In addition, thefourth-generation interchangeable lens 3 will carry out hotlinecommunication with a third-generation camera body 2 in conformance tothe communication specifications designated as the third generation, andwill carry out hotline communication with a fourth-generation camerabody 2 in conformance to the communication specifications designated asthe fourth generation.

It is to be noted that the fourth-generation interchangeable lens 3 mayengage in communication with a second-generation camera body 2 inconformance to the communication specifications designated as the firstgeneration, and may engage in communication with a third-generationcamera body 2 in conformance to the communication specificationrepresented by the first generation or the second generation.Furthermore, it may engage in communication with a fourth-generationcamera body 2 in conformance to the communication specificationsdesignated as the first generation, the second generation or the thirdgeneration.

Next, generation information transmitted from the interchangeable lens 3to the camera body 2 and generation information transmitted from thecamera body 2 to the interchangeable lens 3 through command datacommunication will be explained. In command data communication, dataexpressing lens-side generation information “1”, “2”, “3” or “4” aretransmitted from the interchangeable lens 3 to the camera body 2. Thelens-side generation information “1”, “2”, “3” or “4” indicates that theinterchangeable lens 3 is a first-generation, second-generation,third-generation or fourth-generation interchangeable lens.

It is to be noted that lens-side generation information specifying thefirst generation indicates that the interchangeable lens 3 supports thecommunication specifications designated as the first generation.Likewise, lens-side generation information specifying the secondgeneration indicates that the interchangeable lens 3 supports both thecommunication specifications designated as the first generation and thecommunication specifications designated as the second generation.Lens-side generation information specifying the third generationindicates that the interchangeable lens 3 supports the communicationspecifications designated as any of three generations, i.e., the firstgeneration, the second generation and the third generation, whereaslens-side generation information specifying the fourth generationindicates that the interchangeable lens 3 supports the communicationspecifications designated as any of four generations, i.e., the firstgeneration, the second generation, the third generation and the fourthgeneration.

In addition, as will be explained later, the generation informationtransmitted from the camera body 2 to the interchangeable lens 3specifies a generation, which is determined at the camera body 2 basedupon the lens-side generation information and body-side generationinformation, representing the communication specifications inconformance to which hotline communication is to be carried out by thecamera body 2 and the interchangeable lens 3 mounted at the camera body2. In command data communication, generation information “1” “2”, “3” or“4” is transmitted from the camera body 2 to the interchangeable lens 3.The generation information “1” “2”, “3” or “4” indicates that hotlinecommunication is to be carried out in conformance to the communicationspecifications designated as the first generation, the secondgeneration, the third generation or the fourth generation.

For instance, second-generation information (second generation) may betransmitted from an interchangeable lens 3 supporting up to thesecond-generation communication specifications to a camera body 2supporting up to the second-generation communication specifications. Insuch a case, since the camera body 2 supports the communicationspecifications designated as the matching generation (secondgeneration), information indicating the second generation, i.e., thehighest-order generation, is transmitted to the interchangeable lens 3.By transmitting the matching generation information (second generation)to the interchangeable lens 3, the camera body 2 is issuing a request tothe interchangeable lens 3 that communication be carried out inconformance to the communication specifications represented by thematching generation (second generation).

In addition, an interchangeable lens 3 supporting up to the thirdgeneration communication specifications may be mounted at a camera body2 supporting higher-order generation communication specifications, i.e.,the fourth-generation communication specifications. In this case,generation information indicating the third generation is transmittedfrom the interchangeable lens 3 to the camera body 2 and the camera body2, in turn, transmits generation information indicating thehighest-order generation supported commonly by the camera body 2 and theinterchangeable lens 3, i.e., generation information indicating thethird information, which is a lower generation (lower-order generation)than the generation that the camera body 2 is capable of supporting(fourth generation). The generation information indicating thelower-order generation (third generation) transmitted from the camerabody 2 constitutes a request to the interchangeable lens 3 that hotlinecommunication be carried out in conformance to the communicationspecifications designated as the third generation, which is thehighest-order generation supported by the interchangeable lens 3.

Furthermore, if an interchangeable lens 3 supporting up to, forinstance, the fourth-generation communication specifications is mountedat a third-generation camera body 2, i.e., a lower-order camera body 2,generation information specifying the fourth generation is transmittedfrom the interchangeable lens 3 to the camera body 2. However, thecamera body 2, which does not support the fourth-generationcommunication specifications, transmits generation informationspecifying the third generation, i.e., the highest generation it is ableto support, to the interchangeable lens 3. The generation informationtransmitted from the camera body 2, specifying a lower-order generation(third generation) relative to the communication specifications theinterchangeable lens 3 is able to support, constitutes a request to theinterchangeable lens 3 that hotline communication be carried out inconformance to the communication specifications designated as the thirdgeneration, which is the highest generation that can be supported by thecamera body 2.

As described above, a given generation represents a set of communicationspecifications different from other sets of communicationspecifications. The communication specifications include at least oneitem related to communication, which may be, for instance, thecommunication speed at which hotline communication is carried out, thecommunication interval at which hotline communication is carried out orthe number of sets of data transmitted through hotline communication.Generation information specifies communication specifications inconformance to which the interchangeable lens and the camera body areable to carry out communication through hotline communication.

A method adopted when determining a generation representing thecommunication specifications in conformance to which hotlinecommunication is to be carried out between the interchangeable lens 3and the camera body 2 will be explained below in specific terms.

As the interchangeable lens 3 is mounted at the camera body 2,initialization communication between the interchangeable lens 3 and thecamera body 2 is started through command data communication. As acommand requesting that the lens-side generation information betransmitted is transmitted from the camera body 2 to the interchangeablelens 3 through the initialization communication, the first lenscommunication unit 38 transmits the lens-side generation informationstored in the lens memory 36 to the first body communication unit 28through command data communication. The body control unit 27 obtains thegeneration information pertaining to the mounted interchangeable lens 3via the first body communication unit 28 and ascertains the generationrepresenting the communication specifications that can be supported bythe interchangeable lens 3. For instance, the generation informationpertaining to the interchangeable lens 3 may indicate “3” specifying thethird generation, and in such a case, the body control unit 27ascertains that the interchangeable lens 3 is capable of carrying outhotline communication according to the communication specificationsdesignated as the first generation, the second generation and the thirdgeneration.

The body control unit 27 then determines, based upon the lens-sidegeneration information and the body-side generation information, thegeneration representing the communication specifications in conformanceto which hotline communication is to be carried out, as described below.Namely, the highest-order generation among the generations representingcommunication specifications that can be commonly supported by both theinterchangeable lens 3 and the camera body 2 is selected as thegeneration of communication specifications in conformance to whichhotline communication is to be carried out. For instance, if thelens-side generation information transmitted from the interchangeablelens 3 indicates “3”, i.e., if the interchangeable lens 3 is capable ofcarrying out communication through hotline communication in conformanceto the communication specifications designated as the first generation,the second generation and the third generation as described above andthe body-side generation specifies “4” representing the fourthgeneration, the camera body 2 is able to carry out communication throughhotline communication in conformance to the communication specificationsdesignated as the first generation, the second generation, thethird-generation and the fourth-generation and accordingly, the thirdgeneration, which is the highest-order generation among the generationscommonly supported by both the interchangeable lens 3 and the camerabody 2 will be selected.

As explained above, the body control unit 27 selects the highest-ordergeneration among the generations representing communicationspecifications that can be commonly supported by both theinterchangeable lens 3 and the camera body 2, as indicated in FIG. 7.The body control unit 27 then transmits generation informationspecifying the selected generation to the first lens communication unit38 via the first body communication unit 28. In addition, the bodycontrol unit 27 controls (sets) various components located at the camerabody 2 in correspondence to the communication specifications designatedas the selected generation. As a result, the camera body 2 becomes ableto execute hotline communication with the interchangeable lens 3 mountedthereat in conformance to the communication specifications designated asthe selected generation.

Once a command and data, including the generation information indicatingthe generation of communication specifications for hotlinecommunication, are transmitted from the camera body 2 to theinterchangeable lens 3 through command data communication, hotlinecommunication commences. More specifically, when the camera body 2transmits a command for setting hotline communication to theinterchangeable lens 3, the generation information is also transmittedas a data packet together with the command.

In order to start hotline communication, the lens control unit 37 setsand controls the various components of the interchangeable lens 3 so asto achieve a hotline communication-enabled state in conformance to thecommunication specifications indicated in the generation informationspecifying the generation selected by the camera body 2, i.e., indicatedin the generation information obtained from the camera body 2 via thefirst lens communication unit 38. As a result, the interchangeable lens3 becomes able to execute hotline communication with the camera body 2in conformance to the communication specifications designated as thegeneration selected by the camera body 2. Once a command for settinghotline communication and generation information specifying the firstgeneration or higher are transmitted from the camera body 2 to theinterchangeable lens 3 as described above, the interchangeable lens 3initiates hotline communication. Namely, hotline communication commencesas the command for setting hotline communication and the generationinformation (a value indicating generation information) specifying thecommunication specifications for hotline communication are transmittedfrom the camera body 2 to the interchangeable lens 3.

It is to be noted that the body control unit 27 may select a set ofcommunication specifications different from the communicationspecifications designated as the highest-order generation among thegenerations of communication specifications commonly supported by theinterchangeable lens 3 and the camera body 2. For instance, thecommunication frequency of communication carried out according to thecommunication specifications designated as the highest-order generationmay interfere with the drive frequency at the image sensor or the like,and in such a case, communication may be carried out in conformance tocommunication specifications designated as a lower-order generation soas to prevent such interference.

In the embodiment described above, the interchangeable lens 3 transmitslens-side generation information specifying a generation representing aset of communication specifications that include items such as thecommunication speed and the communication interval, to the camera body2. The camera body 2, having received the lens-side generationinformation, is able to ascertain the communication specifications (thecommunication speed and the like) that can be supported by theinterchangeable lens 3. Since the lens-side generation informationtransmitted from the interchangeable lens 3 to the camera body 2 amountsto a smaller volume of data compared to the volume of data that wouldneed to be transmitted from the interchangeable lens 3 to the camerabody 2 to notify the camera body 2 of the communication speed, thecommunication interval and the like that can be supported by theinterchangeable lens 3 individually through a plurality of communicationsessions, the duration of communication and the number of communicationsessions can both be reduced. In addition, if the communication speed,the communication interval and the like that can be supported by theinterchangeable lens 3 were individually transmitted from theinterchangeable lens 3 to the camera body 2, the camera body 2 wouldneed to verify whether or not there were any inconsistencies in thecommunication speed, the communication interval and the like transmittedfrom the interchangeable lens 3. In the embodiment, each generation(generation information) represents a set of communicationspecifications (communication speed, communication interval and thelike) with no inconsistencies, thereby eliminating the need for the bodycontrol unit 27 to check for any inconsistency in the communicationspeed, the communication interval and the like received from theinterchangeable lens 3.

While an explanation has been given in reference to an example in whichgeneration information specifies the first generation, the secondgeneration, the third generation or the fourth generation, the presentinvention is not limited to this example and generation information mayspecify a fifth or higher-order generation.

In the example explained in reference to FIG. 7, an interchangeable lens3 corresponding to a given generation is able to carry out hotlinecommunication in conformance to the communication specificationsdesignated as a preceding generation (a generation bearing a smallernumber/lower grade), as well. In the example to be described next, theinterchangeable lens 3 is able to carry out hotline communication onlyaccording to the communication specifications corresponding to a singlegeneration and does not support hotline communication according to thecommunication specifications designated as a preceding generation (ageneration bearing a smaller number/lower grade).

FIG. 8 presents a chart indicating generations each representing thecommunication specifications in conformance to which hotlinecommunication is carried out between an interchangeable lens 3, capableof carrying out hotline communication in conformance to thecommunication specifications corresponding to a single generation amongthe first through fourth generations, and a camera body 2 correspondingto a generation among the first through fourth generations. The camerabody 2 is able to carry out hotline communication in conformance to thecommunication specifications designated as a preceding generation (ageneration bearing a smaller number/lower grade), too, as in the exampledescribed in reference to FIG. 7.

FIG. 8 presents a chart indicating generations each representing thecommunication specifications supported in hotline communication carriedout by a specific combination of a camera body 2 and an interchangeablelens 3, with generations pertaining to the camera body 2 indicated alongthe horizontal axis and generations pertaining to the interchangeablelens 3 indicated along the vertical axis. Hotline communication carriedout when an interchangeable lens 3 capable of carrying out hotlinecommunication in conformance to the communication specificationsdesignated as the first generation alone is mounted at the camera body 2corresponding to a certain generation will be explained first. When theinterchangeable lens 3 capable of carrying out hotline communication inconformance to the communication specifications designated as the firstgeneration alone is mounted at a first-generation camera body 2, thefirst lens communication unit 38 transmits lens-side generationinformation “1” to the first body communication unit 28 through commanddata communication executed as the initial communication. The bodycontrol unit 27 receives the lens-side generation information “1” havingbeen transmitted via the first body communication unit 28. The bodycontrol unit 27 at the first-generation camera body 2 selects the firstgeneration, i.e., the highest-order generation among generationscommonly supported by the interchangeable lens 3 and the camera body 2,as the generation representing the communication specifications forhotline communication. The body control unit 27 then transmitsgeneration information specifying the selected first generation to thefirst lens communication unit 38 via the first body communication unit28. Subsequently, hotline communication is carried out between theinterchangeable lens 3 and the camera body 2 in conformance to thecommunication specifications designated as the first generation.

When the interchangeable lens 3, capable of communicating throughhotline communication in conformance to the communication specificationsdesignated as the first generation only is mounted at asecond-generation, third-generation or fourth-generation camera body 2,the first generation, which is the highest-order generation amonggenerations of communication specifications commonly supported by theinterchangeable lens 3 and the camera body 2, is selected as thegeneration representing the communication specifications for hotlinecommunication based upon data exchanged between the interchangeable lens3 and the camera body 2 through command data communication as describedabove, and hotline communication is carried out between theinterchangeable lens 3 and the camera body 2 in conformance to thecommunication specifications designated as the first generation.

Next, hotline communication carried out when an interchangeable lens 3capable of carrying out hotline communication in conformance to thecommunication specifications designated as the second generation aloneis mounted at the camera body 2 corresponding to a certain generationwill be explained. When the interchangeable lens 3 capable of carryingout hotline communication in conformance to the communicationspecifications designated as the second generation alone is mounted at asecond-generation camera body 2, the first lens communication unit 38transmits lens-side generation information “2” to the first bodycommunication unit 28 through command data communication executed as theinitial communication. The body control unit 27 receives the lens-sidegeneration information “2” having been transmitted via the first bodycommunication unit 28. The body control unit 27 at the second-generationcamera body 2 selects the second generation, i.e., the highest-ordergeneration among generations commonly supported by the interchangeablelens 3 and the camera body 2, as the generation representing thecommunication specifications for hotline communication. The body controlunit 27 then transmits generation information specifying the selectedsecond generation to the first lens communication unit 38 via the firstbody communication unit 28. Subsequently, hotline communication iscarried out between the interchangeable lens 3 and the camera body 2 inconformance to the communication specifications designated as the secondgeneration.

When the interchangeable lens 3, capable of communicating throughhotline communication in conformance to the communication specificationsdesignated as the second generation only, is mounted at athird-generation or a fourth-generation camera body 2, the secondgeneration, which is the highest-order generation among generations ofcommunication specifications commonly supported by the interchangeablelens 3 and the camera body 2, is selected as the generation representingthe communication specifications for hotline communication based upondata exchanged between the interchangeable lens 3 and the camera body 2through command data communication as described above, and hotlinecommunication is carried out between the interchangeable lens 3 and thecamera body 2 in conformance to the communication specificationsdesignated as the second generation.

If the interchangeable lens 3, capable of carrying out hotlinecommunication only in conformance to the communication specificationsdesignated as the second generation, is mounted at a first-generationcamera body 2, no common generation of communication specifications issupported by both the interchangeable lens 3 and the camera body 2, andfor this reason, hotline communication will not be carried out in anormal manner or hotline communication will not commence at all.

Next, hotline communication carried out when an interchangeable lens 3capable of carrying out hotline communication in conformance to thecommunication specifications designated as the third generation alone ismounted at the camera body 2 corresponding to a certain generation willbe explained. When the interchangeable lens 3 capable of carrying outhotline communication in conformance to the communication specificationsdesignated as the third generation alone is mounted at athird-generation camera body 2, the first lens communication unit 38transmits lens-side generation information “3” to the first bodycommunication unit 28 through command data communication executed as theinitial communication. The body control unit 27 receives the lens-sidegeneration information “3” having been transmitted via the first bodycommunication unit 28. The body control unit 27 at the third-generationcamera body 2 selects the third generation, i.e., the highest-ordergeneration among generations commonly supported by the interchangeablelens 3 and the camera body 2, as a generation representing thecommunication specifications for hotline communication. The body controlunit 27 then transmits generation information specifying the selectedthird generation to the first lens communication unit 38 via the firstbody communication unit 28. Subsequently, hotline communication iscarried out between the interchangeable lens 3 and the camera body 2 inconformance to the communication specifications designated as the thirdgeneration.

When the interchangeable lens 3, capable of communicating throughhotline communication in conformance to the communication specificationsdesignated as the third generation only, is mounted at afourth-generation camera body 2, the third generation, which is thehighest-order generation among generations of communicationspecifications commonly supported by the interchangeable lens 3 and thecamera body 2, is selected as the generation representing thecommunication specifications for hotline communication based upon dataexchanged between the interchangeable lens 3 and the camera body 2through command data communication as described above, and hotlinecommunication is carried out between the interchangeable lens 3 and thecamera body 2 in conformance to the communication specificationsdesignated as the third generation.

If the interchangeable lens 3, capable of carrying out hotlinecommunication only in conformance to the communication specificationsdesignated as the third generation, is mounted at a first generation orsecond-generation camera body 2, no common generation of communicationspecifications is supported by both the interchangeable lens 3 and thecamera body 2, and for this reason, hotline communication will not becarried out in a normal manner or hotline communication will notcommence at all.

Next, hotline communication carried out when an interchangeable lens 3capable of carrying out hotline communication in conformance to thecommunication specifications designated as the fourth generation aloneis mounted at the camera body 2 corresponding to a certain generationwill be explained. When the interchangeable lens 3 capable of carryingout hotline communication in conformance to the communicationspecifications designated as the fourth generation alone is mounted at afourth-generation camera body 2, the first lens communication unit 38transmits lens-side generation information “4” to the first bodycommunication unit 28 through command data communication executed as theinitial communication. The body control unit 27 receives the lens-sidegeneration information “4” having been transmitted via the first bodycommunication unit 28. The body control unit 27 at the fourth-generationcamera body 2 selects the fourth generation, i.e., the highest-ordergeneration among generations commonly supported by the interchangeablelens 3 and the camera body 2, as a generation representing thecommunication specifications for hotline communication. The body controlunit 27 then transmits generation information specifying the selectedfourth generation to the first lens communication unit 38 via the firstbody communication unit 28. Subsequently, hotline communication iscarried out between the interchangeable lens 3 and the camera body 2 inconformance to the communication specifications designated as the fourthgeneration.

If the interchangeable lens 3, capable of carrying out hotlinecommunication only in conformance to the communication specificationsdesignated as the fourth generation, is mounted at a first-generation,second-generation or third-generation camera body 2, no commongeneration of communication specifications is supported by both theinterchangeable lens 3 and the camera body 2, and for this reason,hotline communication will not be carried out in a normal manner orhotline communication will not commence at all.

In addition, generation information may indicate a value “0”. Generationinformation “0” will not be used to start communication by determining acertain generation of communication specifications in conformance towhich hotline communication is to be carried out between a camera body 2and an interchangeable lens 3, but instead will be used to indicate thathotline communication is not to be executed or to stop hotlinecommunication having been started. Even in the case of a manual focuslens that does not support autofocus operation, a focus lens positionmay be transmitted to the camera body 2 through hotline communication,as long as the position of the manual focus lens can be detected.However, if the interchangeable lens 3 includes a manual focus lenswithout, for instance, a focus lens position detection means, it willnot be necessary in the first place to transmit information indicatingthe focus lens position from the interchangeable lens 3 to the camerabody 2 and thus, it will not be necessary to carry out hotlinecommunication for transmitting the focus lens position information. Whenit is not necessary to transmit information other than the focus lensposition information to the camera body 2, hotline communication doesnot need to be carried out between the interchangeable lens 3 and thecamera body 2, either. Accordingly, if an interchangeable lens 3 thatdoes not support hotline communication, i.e., an interchangeable lens 3in conjunction with which hotline communication does not need to beexecuted, is mounted at the camera body 2, generation informationindicating a value “0” is transmitted from the interchangeable lens 3 tothe camera body 2. In response, the camera body 2 transmits a commandfor setting hotline communication together with a data packet carryinggeneration information specifying a value “0”. The interchangeable lens3, having received the data packet indicating “0” will not start hotlinecommunication with the camera body 2.

Furthermore, the camera body 2 is able to end hotline communication bytransmitting generation information indicating a value “0” to theinterchangeable lens 3. After hotline communication between the camerabody 2 and the interchangeable lens 3 is started, it may be terminatedas power is turned off in response to an operation at a power switch atthe camera body 2, as power is turned off following a non-operatingstate sustained over a predetermined length of time (may otherwise bereferred to as a hibernating state or a sleep state), as an imagereproduction mode is started or as a menu screen is brought up ondisplay. When terminating hotline communication, a command for settinghotline communication and a data packet carrying generation informationindicating a value “0” are transmitted from the camera body 2 to theinterchangeable lens 3. The interchangeable lens 3, which starts hotlinecommunication upon receiving generation information indicating a valueamong “1” through “4” from the camera body 2 through command datacommunication, ends hotline communication upon receiving generationinformation “0” from the camera body 2 through command datacommunication. It is to be noted that the generation informationparameter does not need to specify a value “0” to indicate thatcommunication is not to be started or that communication is to bestopped, and it may instead indicate another predefined value such as“99”.

As described above, generation information may indicate a value(integer) equal to or greater than “0”. As generation informationindicating an integer equal to or greater than “1” is transmitted fromthe interchangeable lens 3 to the camera body 2, the camera body 2selects a corresponding generation representing the communicationspecifications in conformance to which communication can be carried outby the camera body 2, and the interchangeable lens 3 starts hotlinecommunication upon receiving generation information indicating a valueequal to or greater than “1” determined by the camera body 2, togetherwith a command for setting hotline communication.

In addition, if generation information indicating “0” is transmittedfrom the interchangeable lens 3 to the camera body 2, the camera body 2recognizes the interchangeable lens 3 as an interchangeable lens thatcannot be engaged in hotline communication and transmits generationinformation “0” to the interchangeable lens 3.

The interchangeable lens 3 does not start hotline communication afterreceiving a command for setting hotline communication and the generationinformation “0” from the camera body 2. It is to be noted that thecamera body 2, having received generation information indicating “0”from the interchangeable lens 3, does not need to transmit generationinformation “0” or a hotline communication setting command to theinterchangeable lens 3.

Furthermore, once hotline communication starts after the interchangeablelens 3 receives a command for setting hotline communication andgeneration information indicating a value “1” or higher, which has beendetermined at the camera body 2, from the camera body 2, theinterchangeable lens 3 stops the hotline communication upon receivingfrom the camera body 2 a hotline communication setting command andgeneration information “0”.

As described above, the interchangeable lens 3 simply needs to receivefrom the camera body 2 a hotline communication setting command andgeneration information “0” when hotline communication is not to beexecuted or when hotline communication, currently underway, is to bestopped, without requiring a special command for stopping hotlinecommunication. As a result, the number of commands can be reduced. Inaddition, since hotline communication can be started and stopped byusing the same command, control can be simplified.

The generation information, which is transmitted from the camera body 2to the interchangeable lens 3 following a hotline communication settingcommand, indicates that hotline communication is to start, that hotlinecommunication is not to start or that hotline communication havingstarted is to stop, as well as indicating the communicationspecifications in conformance to which hotline communication is to becarried out.

FIG. 9 shows charts presenting an example of hotline communication thatmay be carried out based upon generation information indicating ageneration selected in the camera 1 constituting the image capturingdevice in the first embodiment. An explanation will be given inreference to FIG. 9 by assuming that the focus lens is driven as a drivetarget lens. In FIG. 9, a chart (a) schematically indicates a changeoccurring over time with respect to a position (L1) actually taken bythe focus lens along the optical axis, a chart (b) indicates a pulsesignal output from the encoder in the lens position detection unit 34 asthe focus lens moves, a chart (c) indicates how the lens control unit 37samples the pulse signals, a chart (d) indicates sessions of commanddata communication (CD 1 through CD 3) and hotline communication (HL 1through HL 6) carried out between the camera body 2 and theinterchangeable lens 3 and a chart (e) schematically indicates a changeoccurring over time in a focus lens position (L2) which is reconstructedat the camera body 2 based upon the cumulative value (pulse positioninformation) of pulse signals received through the hotlinecommunication. In FIG. 9, the charts (a) through (e) share a commonhorizontal axis along which time points are indicated.

A curve L1 in the chart (a) in FIG. 9 schematically indicates a changeoccurring over time with respect to the focus lens position with timepoints indicated along the horizontal axis and the position taken by thefocus lens along the optical axis L indicated along the vertical axis.In FIG. 9, the chart (b) indicates a pulse signal output from theencoder in the lens position detection unit 34 explained earlier. Thenumber of these pulse signals corresponds to the distance over which thefocus lens has moved. A pulse signal is generated each time the focuslens is driven to move over a predetermined distance and thus, a greaternumber of pulse signals is generated when the position of the focus lenschanges by a greater extent. This means that when the focus lens movesat a higher traveling speed, pulse signals are generated at higherfrequency. The lens control unit 37 transmits focus lens pulse positioninformation (indicating the focus lens position represented by thecumulative number of pulses) generated by adding up the pulse signalsfrom the interchangeable lens 3 to the camera body 2 through eachsession of hotline communication. It is to be noted that the pulsesignals indicated in the chart (b) may be pulse signals output from thedrive circuit in the lens drive unit 33. A curve L2 in the chart (e) ofFIG. 9 schematically indicates a change occurring over time with respectto the focus lens position reproduced at the camera body 2 based uponthe pulse position information received through each session of hotlinecommunication, with time points indicated along the horizontal axis andthe position of the focus lens along the optical axis L indicated alongthe vertical axis.

It is to be noted that while command data communication and hotlinecommunication are carried out through communication paths different fromeach other, as explained earlier, the chart (d) of FIG. 9 shows sessionsof command data communication (CD1 through CD3) and sessions of hotlinecommunication (HL 1 through HL 6) together. The command datacommunication sessions (CD1 through CD3) are each indicated with adotted-line double-sided arrow, whereas the hotline communicationsessions (HL1 through HL6) are each indicated with a solid-line arrow.Command data communication is bidirectional communication carried outbetween the camera body 2 and the interchangeable lens 3, whereas dataare transmitted from the interchangeable lens 3 to the camera body 2through hotline communication.

In a command data communication session CD1, the lens control unit 37 inthe interchangeable lens 3 transmits the lens-side generationinformation of the interchangeable lens 3 to the first bodycommunication unit 28 at the camera body 2 via the first lenscommunication unit 38. Once the lens-side generation information of theinterchangeable lens 3 is received at the first body communication unit28, the body control unit 27 at the camera body 2 selects a generationrepresenting the communication specifications in conformance to whichhotline communication is to be carried out, as explained earlier, basedupon the lens-side generation information and the body-side generationinformation held in the camera body 2 itself.

In a command data communication session CD2, the first bodycommunication unit 28 transmits a command packet requesting that hotlinecommunication be set and a data packet to the first lens communicationunit 38. This data packet carries generation information indicating thecommunication specifications determined by the body control unit 27.Once the command packet requesting hotline communication be set and thedata packet are received at the first lens communication unit 38, thelens control unit 37 executes processing for setting and controlling thevarious components of the interchangeable lens 3 so as to enablecommunication to be carried out in conformance to the communicationspecifications indicated in the generation information carried in thedata packet.

It is to be noted that through the command data communication sessionCD2, information corresponding to a time shift Δt, which will beexplained later, is transmitted from the interchangeable lens 3 to thecamera body 2.

As indicated in the chart (c) of FIG. 9, the lens control unit 37,having received the command packet requesting the hotline communicationbe set and the data packet (through the command data communicationsession CD2), starts sampling pulse signals output from the lensposition detection unit 34 at a time point t1. The lens control unit 37becomes able to generate pulse signal cumulative value informationindicating the number of pulse signals sampled during a sampling periodby sampling (counting) pulse signals. The second lens communication unit39 shifts into a transmission-enabled state in which it is able totransmit the pulse signal cumulative value (pulse position information)indicating the number of pulse signals, which are counted from theorigin position, and detected via a photo interrupter, to the camerabody 2.

It is to be noted that pulse signal sampling may be started at a timepoint preceding the time point t1 so as to transmit the pulse positioninformation to the camera body 2 at the time point t1 and onwards aftercarrying out CD2.

The first body communication unit 28 transmits a signal carrying a focuslens drive instruction (drive command) to the first lens communicationunit 38 through a command data communication session CD3. The lenscontrol unit 37 starts moving the focus lens based upon the drivecommand.

As indicated in the chart (c) of FIG. 9, the lens control unit 37samples (counts) pulse signals output from the lens position detectionunit 34 over the sampling interval stipulated in the sampling intervalspecifications designated as the generation having been determined. Thelens control unit 37 first samples pulse signals output from the lensposition detection unit 34 during a time period from the time point t1through a time point t2 and generates pulse position informationindicating a cumulative value for the number of sampled pulse signals.The lens control unit 37 subsequently samples pulse signals output fromthe lens position detection unit 34 over the sampling intervalstipulated in the sampling interval specifications designated as thegeneration having been determined beyond the time point t2 as well. Thelens control unit 37 continuously samples pulse signals until itreceives generation information indicating “0” constituting aninstruction for ending the hotline communication as explained earlier.

In a hotline communication session HL1, the second lens communicationunit 39 transmits the pulse signal cumulative value (the pulse signalcumulative value is 1 in the example presented in FIG. 9), indicatingthe number of pulse signals having been sampled during the time periodfrom the time point t1 through the time point t2 to the second bodycommunication unit 29 as pulse position information.

In a hotline communication session HL2, the second lens communicationunit 39 transmits, to the second body communication unit 29, pulseposition information indicating the sum of pulses (the pulse sum isthree in the example presented in FIG. 9), calculated by adding thecumulative value (two pulses in the example presented in FIG. 9)representing the number of pulse signals sampled during a time periodfrom the time point t2 through a time point t3 to the cumulative value(one pulse in the example presented in FIG. 9) representing the numberof pulses sampled during the time period from the time point t1 throughthe time point t2. In each hotline communication session among hotlinecommunication sessions HL3, HL4, HL5, HL6 . . . , the second lenscommunication unit 39 transmits, to the second body communication unit29, pulse position information indicating the pulse value representingthe sum of pulses, calculated by adding the number of pulses sampledduring a time period t3 through t4, t4 through t5, t5 through t6, t6through t7 . . . , to the cumulative number of pulses representing thesum of pulses having been previously sampled.

It is to be noted that the individual sessions of hotline communicationcarried out via the second lens communication unit 39 and the secondbody communication unit 29 are executed at the communication speed andat the communication interval, both stipulated in the communicationspecifications designated as the generation selected by the body controlunit 27, as explained earlier. The hotline communication is carried outat a communication speed of 2.5 MHz at a communication interval of 1msec in the embodiment. Namely, information is transmitted from the lenscontrol unit 37 to the body control unit 27 through sessions HL1, HL2,HL3, HL4, HL5, HL6 . . . , every msec in synchronization with a 2.5 MHzclock frequency.

As described above, the time period from the time point t1 through thetime point t2, the time period from the time point t2 through the timepoint t3, the time period from the time point t3 to the time point t4,the time period from the time point t4 through the time point t5, thetime period from the time point t5 through the time point t6, and thetime period from the time point t6 through the time point t7 each matchwith the sampling interval stipulated in the sampling intervalspecifications designated as the selected generation.

In addition, the interval between the hotline communication sessions HL1and HL2, the interval between the hotline communication sessions HL2 andHL3, the interval between the hotline communication sessions HL3 andHL4, the interval between the hotline communication sessions HL4 andHL5, and the interval between the hotline communication sessions HL5 andHL6 each match with the communication interval stipulated in thecommunication specifications designated as the generation having beenselected. It is to be noted that the sampling interval and thecommunication interval are matching time interval in the embodiment.However, it will be obvious that the sampling interval may be a timeinterval different from the communication interval. For instance, thecommunication interval may be twice as long as the sampling interval.

The sets of pulse position information each indicating a cumulativenumber of pulse signals, repeatedly received at the second bodycommunication unit 29 at the communication interval, are sequentiallystored into the body memory 22 at the camera body 2. The pulse positioninformation is transferred into the body memory 22 through, forinstance, DMA (direct memory access). The body control unit 27references the pulse position information stored in the body memory 22with any timing (e.g., the timing with which a vertical synchronoussignal is output at the image sensor at a time point to following thetime point t6 and preceding the time point t7 in FIG. 9) and thencalculates, through a method to be explained later, the time point(among the time points t2 through t6 on the interchangeable lens-side)at which each set of pulse position information has been generated atthe interchangeable lens 3. The body control unit 27 associates each setof pulse position information with a generation time point at which theparticular set of pulse position information has been generated so as toascertain the positions taken by the focus lens at the individual timepoints, as indicated by the curve L2 in the chart (c) in FIG. 9. It isto be noted that instead of providing pulse position informationindicating the cumulative number of pulse signals as positioninformation repeatedly received at the second body communication unit 29at the communication time interval, pulse signals sampled by the lenscontrol unit 37 at the interchangeable lens 3 during each sampling cyclemay be received at the second body communication unit 29 so as to enablethe body control unit 27 to generate pulse position information bycalculating the cumulative number of pulse signals.

Sets of pulse position information each corresponding to a generatedtime point may be used in, for instance, the phase detection AFmentioned earlier. In such a case, the body control unit 27 calculates adefocus quantity by using focus detection signals output from the imagesensor 21, as explained earlier. The body control unit 27 then generatesa signal carrying an instruction for focus lens drive based upon thedefocus quantity thus calculated and outputs the drive instructionsignal (drive command) having been generated to the lens control unit 37through command data communication. The lens control unit 37 executescontrol for focus lens drive and also transmits pulse positioninformation to the body control unit 27. The body control unit 27ascertains the positions taken by the focus lens at the various timepoints based upon the pulse position information and determines theexact position to which the focus lens has moved relative to the focuslens traveling distance (defocus quantity) having been specified to thelens control unit 37.

Furthermore, the sets of pulse position information each correspondingto a certain generated time point may be used in contrast AF mentionedearlier. In such a case, based upon the generated time points at whichthe individual sets of pulse position information have been generatedand generated time points at which signals, each used for purposes ofcontrast evaluation value calculation, have been generated at the imagesensor 21, the body control unit 27 associates each set of pulseposition information indicating a focus lens position with a contrastevaluation value. As a result, the body control unit 27 is able toascertain the focus lens position and the contrast evaluation valuecorresponding to each time point. The body control unit 27 thencalculates the focus lens pulse position at which a peak contrastevaluation value is achieved as an in-focus position. The body controlunit 27 generates a signal carrying a focus lens drive instruction basedupon the in-focus position thus calculated and outputs the driveinstruction signal (drive command) thus generated to the lens controlunit 37 through command data communication. The lens control unit 37adjusts the focusing condition by executing drive control for moving thefocus lens to the in-focus position.

An offset that may occur with respect to the lens position reproduced atthe camera body 2 due to a shift in the clock timing at the camera body2 relative to the clock timing at the interchangeable lens 3 will beexplained next. The camera body 2 and the interchangeable lens 3 areengaged in operation on separate clocks. Namely, the camera body 2generates a clock to be used within the camera body 2, whereas theinterchangeable lens 3 generates its own clock to be used within theinterchangeable lens 3. The frequency of the clock used within thecamera body 2 and the frequency of the clock used within theinterchangeable lens 3 may be matching frequencies or they may befrequencies different from each other. Assuming that the frequency ofthe clock generated in the camera body 2 is the same as the frequency ofthe clock generated in the interchangeable lens 3 and that the clocktiming (the rise and the fall of the clock) of one clock is in completesynchronization with the clock timing of the other clock, the camerabody 2 is able to accurately ascertain a generated time point at which asignal has been generated in the interchangeable lens 3. However, if theclock timing at the camera body 2, i.e., the clock frequency and thetiming with which the clock rises/falls, is different from the clocktiming in the interchangeable lens 3, the camera body 2 is not able toaccurately ascertain a time point at which a signal has been generatedat the interchangeable lens 3, resulting in a time shift occurring withrespect to the actual lens position and the lens position reproduced atthe camera body 2.

The following is an explanation of a method adopted in the camera body 2to calculate a time point (among the time points t2 through t6 on theinterchangeable lens-side) at which a set of pulse position information(a cumulative value of pulse signals) has been generated at theinterchangeable lens 3 when the clock timing in the camera body 2 andthe clock timing in the interchangeable lens 3 are different. As hasbeen explained in reference to the charts (b) through (d) in FIG. 9,sets of pulse position information are generated as the lens controlunit 37 samples pulse signals output from the lens position detectionunit 34 or the lens drive unit 33 over a predetermined cycle. The lenscontrol unit 37 samples pulse signals in response to a clock signal usedwithin the interchangeable lens 3 (hereafter will be referred to as alens clock signal). Namely, the time points t2, t3, t4, t5, t6, t7, . .. , at each of which a pulse signal is sampled and informationindicating the cumulative value of pulse signals is generated in FIG. 9are in synchronization with a rise or a fall of the lens clock signal.This lens clock signal is different from the CLK signal provided fromthe camera body 2.

The body control unit 27 ascertains a time point at which pulse signalsampling has started in reference to, for instance, the time point atwhich the command data communication session CD2 has been carried outfor purposes of setting hotline communication. In order to enable thebody control unit 27 to ascertain the time point at which theinformation indicating the cumulative value of pulse signals wasgenerated at the lens control unit 37 relative to the time point atwhich the command data communication session CD2 was executed, the lenscontrol unit 37 calculates the length of time having elapsed between thetime point at which the command data communication session CD2 wasexecuted and the time point t1 at which the pulse signal samplingstarted (the time shift Δt indicated in the chart (d) in FIG. 9) througha method to be explained later. The lens control unit 37 transmitsinformation corresponding to the time shift Δt having been calculated tothe camera body 2 through the command data communication session CD2.

The body control unit 27 at the camera body 2 obtains the informationcorresponding to the time shift Δt transmitted from the interchangeablelens 3 and calculates a time point at which the pulse positioninformation, indicating the cumulative value of pulse signals, wasgenerated relative to the time point of the data transmission throughthe command data communication CD2 by using the time shift Δt. The bodycontrol unit 27 thus calculates the pulse position information generatedtime point in reference to the transmission time point at which thecommand data communication CD2 was carried out.

FIG. 10 is a chart in reference to which a method that may be adoptedwhen calculating the time shift Δt in the image capturing device in thefirst embodiment will be explained. It is to be noted that at time pointt−1, a time point t0, a time point t1 and a time point t2 in FIG. 10respectively correspond to the time point t−1, the time point t0, thetime point t1 and the time point t2 in FIG. 9. A command packet 44 and adata packet 45 are a command packet and a data packet transmitted fromthe camera body 2 to the interchangeable lens 3 through the command datacommunication session CD2 in FIG. 9. The command packet 44 carries ahotline communication setting instruction signal whereas the data packet45 carries a signal that includes the generation information indicatingthe generation having been selected at the camera body 2.

Trigger signals used to latch pulse signals, indicated at the timepoints t−1, t1 and t2 in FIG. 10, are repeatedly generated at apredetermined cycle S based upon the lens clock signal output from thelens control unit 37 in the interchangeable lens 3. The predeterminedcycle S matches the sampling interval in the chart (c) in FIG. 9, whichis specified in the generation information as the sampling interval, ashas been explained in reference to FIG. 6. The lens control unit 37samples (latches) pulse signals output from the lens position detectionunit 34 or the lens drive unit 33 over the sampling interval S by usingthe trigger signals.

A method that may be adopted when calculating the time shift Δt will bedescribed next. The following explanation will be given on the premisethat once the interchangeable lens 3 is mounted at the camera body 2 andpower supply from the camera body 2 starts, the lens control unit 37starts latching pulse signals over the sampling interval S stipulated inthe specifications it is capable of supporting. FIG. 10 shows processingexecuted over a span of time including and following the latching timepoint t−1 immediately before the command data communication session CD2starts. After setting the RDY signal to high level upon receiving thecommand packet 44 normally through the command data communication CD2,the lens control unit 37 switches the RDY signal to low level at thetime point t0. The lens control unit 37 detects the length of timeelapsing between the time point t−1 and the time point t0 and calculatesthe time shift Δt by subtracting the length of time elapsing between thetime point t−1 and the time point t0 from the cycle S spanning from thetime point t−1 through the time point t1. In more specific terms, thelens control unit 37 counts, via a built-in counter circuit or the like,lens clock signals over the period of time between the time point t−1 toa falling edge of the RDY signal so as to detect the length of timeelapsing between the time point t−1 and the time point t0. The lenscontrol unit 37 then outputs information indicating the time shift Δt tothe body control unit 27 through the command data communication CD2.

In addition, upon receiving the data packet 45, the lens control unit 37shifts the RDY signal from low level to high level. The lens controlunit 37 also starts hotline communication in conformance to thecommunication specifications designated as the generation having beenselected at the camera body 2, as indicated in the generationinformation carried in the data packet 45, as explained earlier. Thelens control unit 37 further generates trigger signals at the samplinginterval S as stipulated in the sampling interval specificationsdesignated as the generation having been selected so as to engage inpulse signal sampling processing (see FIG. 9). The lens control unit 37counts pulse signals from the lens position detection unit 34 or thelens drive unit 33 generated during the cycle S spanning from the timepoint t1 to the time point t2. Information indicating the number ofsampled pulse signals is transmitted from the interchangeable lens 3 tothe camera body 2 through the hotline communication session HL1 in FIG.9.

The body control unit 27 obtains the information indicating the timeshift Δt from the lens control unit 37 through the command datacommunication CD2. The body control unit 27 calculates the pulseposition information generated time point, i.e., the time point at whichpulse signals output from the encoder in the lens position detectionunit 34 or the lens drive unit 33 have been sampled, based upon the timeshift Δt and the sampling interval S. For instance, the body controlunit 27 may calculate (determine) the pulse position informationgenerated time point t2 as a time point t0+Δt+S by adding the time shiftΔt and the sampling interval S to the RDY signal fall time point t0. Inaddition, the body control unit 27 calculates pulse position informationgenerated time points t3, t4, t5 and t6 respectively as; t2+S, t2+2S,t2+3S and t2+4S.

The camera body 2 in the embodiment obtains the time shift Δt pertainingto a time point at which pulse position information, indicating thecumulative number of pulse signals, is generated and generates throughcalculation focus lens position information by using the time shift Δt.As a result, the extent of temporal delay occurring with respect to thefocus lens position reproduced through calculation at the camera body 2and the actual position of the focus lens at the interchangeable lens 3,can be reduced. The following is an explanation of this reduction in thetemporal delay (cancellation of the time shift Δt causing the delay)between the reproduced focus lens position and the actual focus lensposition, given by contrasting it with a comparison example.

In the comparison example, a focus lens position is calculated withoutascertaining an accurate time shift Δt. Since the accurate time shift Δtis not provided by the lens control unit 37, the body control unit 27calculates a lens position information generated time point by using afixed value as an equivalent to the time shift instead. However, sincethe lens position information is generated by using trigger signals(signals generated based upon the lens clock signal used within theinterchangeable lens 3) which are asynchronous with respect to the clocksignal (CLK signal) provided from the camera body 2, the time shift isbound to change in correspondence to the timing with which the hotlinecommunication setting instruction command is transmitted from the camerabody 2 (the timing with which the RDY signal falls in the embodimentdescribed in reference to FIG. 10). As a result, the use of the fixedvalue as an equivalent the time shift is bound to cause an error whensetting sets of pulse position information in correspondence toindividual pulse position information generated time points, which, inturn, is bound to result in a difference between the actual focus lensposition and the calculated focus lens position. It is to be noted thata clock signal for hotline communication (HCLK signal), generated basedupon the lens clock signal, is output from the interchangeable lens 3 tothe camera body 2.

In the embodiment, in which the focus lens position is reproduced byusing the time shift Δt representing the difference between the timingwith which the command signal is transmitted and the timing with whichthe lens control unit 37 actually measures (samples) pulse signals, theextent of temporal offset with respect to the reproduced focus lensposition and the actual focus lens position is reduced. As a result, theoccurrence of an error that could otherwise occur when, for instance,determining a focus lens position to be designated as the in-focusposition through autofocus can be prevented.

The following advantageous operations are achieved through theembodiment described above.

(1) Generation information indicating the communication specificationsfor hotline communication is transmitted from the interchangeable lens 3to the camera body 2 through command data communication. Thus, thecamera body 2 is able to ascertain the communication specifications(including the communication speed) that can be supported by theinterchangeable lens 3 by referencing the generation informationtransmitted from the interchangeable lens 3 through command datacommunication. As a result, optimal communication can be carried outbetween the camera body 2 and the interchangeable lens 3. In addition,since the data transmitted through hotline communication, such asinformation pertaining to focus lens drive (information related to thefocus lens position and the like) and information pertaining toanti-vibration lens drive (information related to the anti-vibrationlens position and the like) as well as the data indicating thecommunication speed and the communication interval, are not separatelyand individually transmitted from the interchangeable lens 3 to thecamera body 2, the volume of data transmitted from the interchangeablelens 3 to the camera body 2 can be reduced and furthermore, the lengthof communication time and the number of communication sessions requiredto determine a set of communication specifications through communicationbetween the interchangeable lens 3 and the camera body 2 can be reduced.The number of values indicated in the generation information is smallerthan the number of all the combinations of sets of communicationspecifications or data that may be indicated in the generationinformation. Moreover, if the individual communication specificationitems (the communication speed, the communication interval and the like)and sampling interval specification items indicated in the generationinformation in the embodiment were separately transmitted from theinterchangeable lens 3 to the camera body 2, the camera body 2 wouldneed to check and verify to ensure that there were no inconsistenciesamong the individual sets of information. In the embodiment, a set ofcommunication specifications (the communication speed, the communicationinterval and the like) and a set of sampling interval specificationsachieving consistency are set and generation information indicatingthese specifications is stored. Thus, the camera body 2, having receivedthe generation information, is not required to check the specificationsto ensure that there is no inconsistency.

In addition, the interchangeable lens 3 transmits, to the camera body 2,information (lens position information) pertaining to a drive targetmember (e.g., the focus lens), generated by a generating unit (lenscontrol unit 37), through hotline communication executed in conformanceto the communication specifications designated as the generationselected by the camera body 2. This means that the position informationwith respect to a drive target member such as the focus lens can betransmitted at high speed from the interchangeable lens 3 to the camerabody 2 through hotline communication, which, in turn, makes fasterautofocus operation possible.

(2) The interchangeable lens 3 includes the lens control unit 37 thatrepeatedly generates information (lens pulse position information)pertaining to a drive target member (such as the focus lens), transmitsthe information to the camera body 2, calculates a time shift Δtelapsing from a time point at which a communication start instructionsignal from the camera body 2 is received through a time point at whichinformation pertaining to the drive target member is generated at thelens control unit 37 and transmits information indicating the time shiftΔt to the camera body 2. Thus, the camera body 2 is able to ascertainpositions taken by the focus lens at various time points based upon thelens pulse position information and the time shift Δt. Moreover, thecamera body 2 in the embodiment reproduces/generates a focus lensposition based upon the time shift Δt. Consequently, deviation of thefocus lens position reproduced at the camera body 2 relative to theactual focus lens position at the interchangeable lens 3 can be reduced.

(3) The CLK terminal is disposed at a position set apart from the VBATterminal by a greater distance compared to the GND terminal. Inaddition, the PGND terminal is disposed between the GND terminal and theVBAT terminal. This makes it possible to shield the CLK terminal,through which a clock signal used in command data communication istransmitted, from noise originating at the VBAT terminal. As a result,the command data communication can be carried out in a stable manner.Consequently, generation information can be transmitted/received betweenthe camera body 2 and the interchangeable lens 3 in a reliable manner.

The following variations are also within the scope of the presentinvention, and one of the variations or a plurality of variations may beadopted in combination with the embodiment described above.

Variation 1

In the embodiment described above, full duplex communication is executedas the command data communication carried out via the first lenscommunication unit 38 and the first body communication unit 28. As analternative, half duplex communication may be executed as the commanddata communication carried out between the first lens communication unit38 and the first body communication unit 28.

Variation 2

In the embodiment described above, the lens control unit 37 calculatesthe time from the time point t0 through the time point t1 in FIG. 10 asa time shift Δt and the body control unit 27 calculates a lens positioninformation generated time point based upon the time shift Δt calculatedby the lens control unit 37. Instead, the lens control unit 37 maycalculate the length of time elapsing from the time point t0 to the timepoint t2 in FIG. 10 (i.e., a time shift Δt2) and output the time shiftΔt2 to the camera body 2. In such a case, the body control unit 27 willcalculate a lens position information generated time point by using thetime shift Δt2.

For instance, the body control unit 27 will calculate (determine) a lensposition information generated time point t2 as a time point t0+Δt2 byadding the time shift Δt2 to the RDY signal fall time point t0. The bodycontrol unit 27 will also calculate lens position information generationtime points t3, t4, t5 and t6 respectively as t2+S, t2+2S, t2+3S andt2+4S.

Variation 3

While the lens control unit 37 in the embodiment described aboveincludes the first lens communication unit 38 and the second lenscommunication unit 39, it does not need to include two separatecommunication units and may instead carry out communication via a singlelens communication unit. While the body control unit 27 includes thefirst body communication unit 28 and the second body communication unit29, it does not need to include two separate communication units and mayinstead carry out communication via a single body communication unit.

Variation 4

While an interchangeable lens is mounted as a camera accessory in theembodiment described above, an accessory other than an interchangeablelens may be mounted. The accessory may be, for instance, atele-converter, a wide-angle converter or a close-up ring mountedbetween the camera body and an interchangeable lens, which is used toadjust the focal length of the interchangeable lens. The presentinvention may be further adopted in conjunction with, for instance, amount adapter that allows an accessory such as an interchangeable lenscompatible with a mount standard different from the camera body mountstandard to be mounted. Namely, the present invention may be adopted inmuch the same way in conjunction with any accessory that is mounted atthe camera body mount. An accessory-side terminal group, accessory-sideprojecting portions, accessory-side communication units and the like ofsuch an accessory will be equivalent to the lens-side terminal group,the lens-side claw portions 139, the first and second lens communicationunits 38 and 39 and the like respectively.

While the embodiment has been described in reference to an accessorythat can be mounted at a camera body, the present invention may beadopted in conjunction with a mount adapter instead of a camera body,that allows an interchangeable lens compatible with the mount standarddescribed above to be mounted at a camera body that is not compatiblewith the mount standard by mounting the accessory via the mount adapter.

Variation 5

The interchangeable lens 3 in the embodiment described above transmitsinformation to the camera body 2 over the communication intervalindicated in the communication specifications designated as thegeneration having been selected. However, the interchangeable lens 3does not always need to transmit data over the communication intervalstipulated in the communication specifications designated as theselected generation. The interchangeable lens 3 may instead transmitdata over a communication interval that is an integer multiple of thecommunication interval stipulated in the communication specificationsdesignated as the selected generation, e.g., twice the communicationinterval stipulated in the communication specifications designated asthe selected generation. In such a case, the camera body 2 will be ableto receive all the data transmitted from the interchangeable lens 3 overan interval twice as long as the communication interval stipulated inthe communication specifications designated as the selected generation.However, it will be obvious that data having been generated may betransmitted on an irregular basis instead of over the communicationinterval twice the length of the stipulated communication interval orover any cycle, as long as the data are synchronized with thecommunication interval stipulated in the communication specificationsdesignated as the selected generation. Moreover, the interchangeablelens 3 may transmit data over a communication interval three times thelength of the communication interval stipulated in the communicationspecifications designated as the selected generation.

While an embodiment and variations thereof have been described above,the present invention is in no way limited to the particulars of theseexamples. The embodiment and any of the variations may be adopted incombination. Furthermore, any other mode conceivable within the scope ofthe technical teachings of the present invention is also within thescope of the present invention.

REFERENCE SIGNS LIST

1 . . . camera (camera system), 2 . . . camera body, 3 . . .interchangeable lens, 27 . . . body control unit, 28 . . . first bodycommunication unit, 29 . . . second body communication unit, 37 . . .lens control unit, 38 . . . first lens communication unit, 39 . . .second lens communication unit

The invention claimed is:
 1. An accessory that is mountable at a camerabody and is capable of communicating with the camera body, the accessorycomprising: a processor programmed to: transmit a first clock signal tothe camera body; transmit to the camera body information pertaining to adrive target member that is driven by a drive unit in synchronizationwith the first clock signal; receive a second clock signal from thecamera body; transmit to the camera body a first value indicating acommunication specification according to which the processor transmitsthe information to the camera body in synchronization with the secondclock signal; receive from the camera body a second value equal to orsmaller than the first value in synchronization with the second clocksignal, the second value indicating a communication specificationaccording to which the processor transmits the information to the camerabody; and start transmitting the information according to thecommunication specification indicated by the second value, uponreceiving the second value after the first value has been transmitted.2. The accessory according to claim 1, wherein: the information isposition information pertaining to a position of the drive targetmember.
 3. The accessory according to claim 1, wherein: the processorreceives the second value which is determined at the camera body basedupon the first value transmitted.
 4. The accessory according to claim 1,wherein: the first value indicates that the processor is capable oftransmitting the information to the camera body according to thecommunication specification indicated by a value equal to or smallerthan the first value.
 5. The accessory according to claim 1, wherein:the processor receives a command signal from the camera body; and theprocessor starts transmitting the information according to thecommunication specification indicated by the second value afterreceiving the command signal and the second value from the camera body.6. The accessory according to claim 5, wherein: the command signalcarries a command for the processor to set the communicationspecification indicated by the second value.
 7. The accessory accordingto claim 5, wherein: upon receiving the command signal and a third valueafter starting transmitting the information, the processor stopstransmission of the information.
 8. The accessory according to claim 7,wherein: the third value is
 0. 9. The accessory according to claim 1,wherein: the first value and the second value each represent generationinformation indicating a communication specification according to whichcommunication is carried out between the accessory and the camera body.10. The accessory according to claim 1, wherein: the communicationspecification includes a specification pertaining to a communicationspeed at which, or a communication interval over which, the processortransmits the information to the camera body.
 11. An accessory that ismountable at a camera body and includes a plurality of terminals viawhich communication is carried out with the camera body, comprising: afirst terminal through which a first clock signal is output to thecamera body; a second terminal through which information pertaining to adrive target member that is driven by a drive unit is output to thecamera body in synchronization with the first clock signal; a thirdterminal through which a second clock signal is input from the camerabody; a fourth terminal through which a first value is transmitted tothe camera body in synchronization with the second clock signal, thefirst value indicating a communication specification according to whichthe information is transmitted through the second terminal to the camerabody; a fifth terminal through which a second value is received from thecamera body in synchronization with the second clock signal after thefirst value is transmitted through the fourth terminal, the second valueindicating a communication specification according to which theinformation is transmitted through the second terminal to the camerabody; a sixth terminal used to indicate whether or not communicationwith the camera body is enabled; a seventh terminal through which asecond source voltage from the camera body is supplied; an eighthterminal used as a ground potential for the second source voltage; aninth terminal through which a first source voltage from the camera bodyis supplied; a tenth terminal used as a ground potential for the firstsource voltage; an eleventh terminal used for the camera body to detectthat the accessory is mounted; and a control unit that startstransmission of the information through the second terminal according tothe communication specification indicated by the second value uponreceiving the second value through the fifth terminal.
 12. The accessoryaccording to claim 11, wherein: the information is position informationpertaining to a position of the drive target member.
 13. The accessoryaccording to claim 11, wherein: the fifth terminal receives the secondvalue determined at the camera body based upon the first value havingbeen transmitted through the fourth terminal.
 14. The accessoryaccording to claim 11, wherein: the first value indicates that theinformation can be transmitted to the camera body through the secondterminal according to the communication specification indicated by avalue equal to or smaller than the first value.
 15. The accessoryaccording to claim 11, wherein: the fifth terminal receives a commandsignal from the camera body; and the control unit starts transmission ofthe information through the second terminal according to thecommunication specification indicated by the second value upon receivingthe command signal and the second value from the camera body through thefifth terminal.
 16. The accessory according to claim 15, wherein: thecommand signal carries a command for the control unit to set thecommunication specification indicated by the second value.
 17. Theaccessory according to claim 15, wherein: upon receiving the commandsignal and a third value after transmission of the information throughthe second terminal starts, the control unit stops the transmission ofthe information through the second terminal.
 18. The accessory accordingto claim 17, wherein: the third value is
 0. 19. The accessory accordingto claim 11, wherein: the first value and the second value eachrepresent generation information indicating a communicationspecification according to which communication is carried out betweenthe accessory and the camera body.
 20. The accessory according to claim11, wherein: the communication specification include a specificationpertaining to a communication speed or a communication intervalpertaining to communication via the terminals.